The origin of ancient Chinese metrology can be traced back to the ancient times four or five thousand years ago. Initially, our ancestors created counting and measuring methods in production practice, such as "recording events by tying knots", "measuring length with hands (spreading hands to know the ruler)", "measuring volume by holding (cupping hands to make a sheng)", "measuring mu by stepping (striding to determine mu)", and "timing by dripping water". The earliest written record appears in *Shangshu·Shundian (Book of Documents·Canon of Shun)*: "Coordinate the seasons, months, and correct the days; unify the temperament, weights, and measures." What were the measuring tools in different periods? What was the most special tool? What kind of evolution did they go through? ### Measuring Tools in Different Periods #### Huangdi Established the "Five Measures" Xia, Shang, and Zhou Dynasties: *Records of the Grand Historian·Da Dai Liji* records that during the period of Huangdi (the Yellow Emperor), five measures were established: du (length), liang (volume), heng (weight), li (mu, area), and shu (number). In short, in ancient times, the function of weights and measures was concentrated on an experiential recognition of production processes and methods. It was carried out sporadically by people at that time to adapt to nature and continuously adjust production activities, belonging to the spontaneous and embryonic stage of the development of weights and measures. #### Shang Yang Sheng Spring and Autumn and Warring States Periods: All vassal states regarded the promulgation of weights and measures systems as a national strategy and formed certain management systems. At that time, manually made standard measuring instruments appeared, among which the more famous ones were Shang Yang sheng (a volume-measuring vessel) and Qi Zihe Fu (a vessel for measuring grain). Some vassal states also stipulated that the second month of spring and the second month of autumn were the times for checking weights and measures. #### Qin Liang (Qin Dynasty Volume-Measuring Vessel) Qin Dynasty: After Emperor Qin Shi Huang unified the country, he unified weights and measures, supervised the production of a large number of standard weights and measures instruments, and distributed them across the country. At present, sixty to seventy Qin quan (weights) and Qin liang (volume vessels) have been collected in China, made of pottery, iron, and copper. Through actual measurement, the unit values of Qin quan and Qin liang are relatively unified, and most errors do not exceed the range allowed by *Xiao Lv (Laws on Effectiveness)*. #### Xin Mang Tong Jialiang (Bronze Standard Measuring Vessel of the Xin Dynasty) Late Western Han Dynasty: Wang Mang usurped the Liu family's throne and established the Xin Dynasty. Liu Xin, the state teacher of Wang Mang, designed and manufactured the Xin Mang Tong Jialiang, which was modeled after the Lishi Liang (a measuring vessel from the Zhou Dynasty). The Xin Mang Tong Jialiang designed by Liu Xin reflected the scientific and technological level of that time. During the Xin Mang period, a copper caliper was also designed and made to measure the diameter of spheres, and it also provided a simple and accurate measuring tool for measuring the depth and end face of containers. #### Guanghe Dasinong Tong Hu (Bronze Hu of the Grand Minister of Agriculture in the Guanghe Period) Eastern Han Dynasty: The "Guanghe Dasinong" Tong Hu of the Eastern Han Dynasty is in the shape of a round barrel, 24.4 cm high, with a caliber of 34.5 cm, and symmetric short handles on the left and right sides of the belly. The measured volume is 19,600 ml, which is equivalent to 196 ml per sheng. #### Tigan Cheng (Lever Scale) Wei, Jin, and Southern and Northern Dynasties: During the Southern and Northern Dynasties, the quanheng (balance) was continuously improved and perfected in use, gradually evolving into the tigan cheng (lever scale). This brought an important transformation to the ancient "heng (balance beam)", making measurement more convenient and accurate compared with the original heng. #### Square Jialiang of the Tang Dynasty Tang Dynasty: A square Jialiang appeared in the Tang Dynasty. The square Jialiang overcame the unavoidable systematic errors of the round Jialiang. On the other hand, the geometric dimensions of the square Jialiang were easy to grasp, which was beneficial for local governments to copy according to the drawings, popularize them, and ensure the quality of value transmission. #### Song Dynasty Dengcheng (Small Steelyard) Song Dynasty: During the Jingde period, Liu Chenggui, an official in charge of the Neicangku (Inner Storage Warehouse), created two small and precise dengcheng as national weight standards: one used a decimal system of liang (tael), qian (mace), fen (candareen), and li (milli-candareen), with a maximum weighing capacity of one and a half qian and a division value of one li; the other used a non-decimal system of liang, zhu (铢), lei (累), and shu (millet), with a maximum weighing capacity of one liang and a division value of one lei. The two could be cross-checked to obtain liang, qian, and fen. #### Guo Shoujing's Measuring Instruments Yuan Dynasty: *Yuan Shi (History of the Yuan Dynasty)* records that measuring instruments such as the "Fangzheng An (square and upright table, created by Guo Shoujing)" were used to accurately "measure shadows and determine directions" across the country, including terrain (horizon angle) and altitude. Detailed requirements were set for the use of measuring instruments such as the "Fangzheng An", stipulating that "all uses shall be based on this standard". #### Ming Dynasty Baochao (Paper Money) Ming Dynasty: In addition to the government's regular calibration of weights and measures according to laws, ordinary people often used Baochao (paper money) as a reference to protect their own interests. *Lülü Jingyi (Essentials of Pitch Pipes)* of the Ming Dynasty records: "The Chao Chi (paper money ruler, i.e., tailor's ruler) is aligned with the outer edge of the paper money. The Qu Chi (curved ruler, i.e., construction ruler, metric ruler) is aligned with the outer edge of the inked part of the Baochao; the Baoyuan Ju Tong Chi (copper ruler of the Baoyuan Bureau, i.e., land-measuring ruler) is longer than the inked edge of the Baochao but shorter than the paper edge, equivalent to 9.6 cun of the tailor's ruler." This shows that the size of Ming Baochao was relatively stable and could win people's trust. #### Qing Dynasty Yingzao Chi (Construction Ruler) Qing Dynasty: Emperor Kangxi personally determined the ruler by arranging millet grains, defining the length of 100 vertically arranged millet grains as the Yingzao Chi (construction ruler). He also established the volume of measuring vessels based on certain dimensions, cast a Cao Hu (grain transportation hu) with iron, and used the weight of one cubic cun of metal as the mass standard. From this, the sizes of various weight砝码 (weights) were determined as the standard instruments for weighing national treasury revenues and expenditures, hence called Kuping (treasury standard). The weights and measures system composed of Yingzao Chi, Cao Hu, and Kuping Liang (treasury standard tael) was simply called the Yingzao Kuping system, thus establishing a mutual calibration relationship among the three aspects of weights and measures. ### Ancient Measuring Tool "Quanheng" Among these measuring tools, there is a very special one. The profoundness of Chinese culture is incomparable to alphabet-based languages. For example, the character "quan (权)" today basically refers to "power", such as "regime", "right", "abstention", "authority", "authorization", "hold power", etc. Among the idioms related to "quan", "quanheng libi (权衡利弊)" comes first. In Chinese, it is explained as: Quan: weight (of a balance). Heng: balance beam. Quanheng: compare, weigh. Compare which is beneficial and which is harmful. According to *Qian Han·Lv Li Zhi (Book of Han·Treatise on Pitch Pipes and Calendars)*: "Heng is balance. It is used to hold the quan and equalize things, balancing weights." *Liji·Shenyi (Book of Rites·Deep Robe)* says: "Compasses and squares symbolize selflessness; the plumb line symbolizes straightness; quanheng symbolizes fairness." The general idea of this passage is: Conforming to compasses and squares symbolizes impartiality and selflessness; being as vertical as a plumb line symbolizes integrity; being as balanced as the weight and beam of a scale symbolizes fairness. *Records of the Grand Historian·Biography of Fan Ju and Cai Ze* also says: "Level the quanheng, correct the measures, and adjust the weights." Zhuangzi said in *Wai Pian·Quqie (Outer Chapters·Opening Trunks)*: "People make dou and hu to measure things, but then others steal the dou and hu along with the things; people make quanheng to weigh things, but then others steal the quanheng along with the things; people make tallies and seals to authenticate things, but then others steal the tallies and seals along with the authentication; people make benevolence and righteousness to rectify things, but then others steal benevolence and righteousness along with the rectification." In this article, Zhuangzi fiercely criticized the powerful minister Tian Chengzi, saying, "Those who steal a hook are executed; those who steal a state become feudal lords." In his view, "quanheng" was a crucial instrument of the state, sacred and inviolable. In short, "quanheng" is a balance. In ancient China, balances and steelyards for weighing things were collectively called "quanheng". The ancients regarded quanheng as a symbol of fairness and impartiality. Next, let's elaborate on "quanheng". #### 1. "Quanheng" was a Crucial Instrument of the State Western Zhou bronze wares are inscribed with characters such as "jin shi lve (金十寽)" and "si san lve (丝三寽)", "jin shi yun (金十匀)". Here, "jin (金)" does not refer to gold but copper; "lve (寽)" and "yun (匀)" are units of measurement. From these inscriptions, we can know that as early as the Western Zhou Dynasty, people had mastered the lever principle and made "quanheng"—a tool for weighing the mass of objects, i.e., a balance. The steelyard emerged during the Wei, Jin, and Southern and Northern Dynasties. By the Three Kingdoms period, the lifting button of the balance gradually moved from the middle to one end, and there were scale marks carved on the heng (beam) to calculate jin (catty) and liang (tael). This was the prototype of the lifting lever steelyard. Judging from the iron weights unearthed from the Northern Wei and Northern Qi dynasties, steelyards had been popularized and widely used among the people as early as the Wei, Jin, and Southern and Northern Dynasties. In 1973, a Qin Dynasty iron quan was unearthed in Qingshan. From the inscriptions, we know that as a standard weight approved by the Qin government, this iron quan was a measuring tool uniformly cast when Emperor Qin Shi Huang unified weights and measures. Only two such iron quan exist in the country, making them rare cultural relics. The inscription reads: "In the 26th year of the emperor's reign, he unified all under heaven; the nobles and common people are greatly peaceful. He established the title of emperor and then ordered Prime Ministers Zhuang and Wan to standardize weights and measures. All those that were inconsistent and doubtful were clearly unified." In March 2015, a bronze quan with a history of thousands of years was found in the cultural relics unearthed from a residual Eastern Han earthen tomb in Yuanqu County, Shanxi Province. As a physical object, it can prove the history of ancient Chinese weights and measures and bronze ware development. Weighing and measuring instruments were crucial state instruments, and each dynasty attached great importance to their production and management. As early as the Western Zhou Dynasty, King Cheng of Zhou issued standards for weights and measures and made special regulations on their use and management: every second month of spring and autumn, "unify measures and level quanheng". According to *Qin Lv·Gong Lv (Qin Laws·Work Laws)*, the law stipulated that weighing instruments should be calibrated once a year. When receiving or borrowing them, they must be calibrated on the spot before being handed over to the recipient. During the reign of Emperor Zhenzong of the Song Dynasty, weights and measures were calibrated again. To strengthen the management of weighing instruments, successive dynasties also set up special officials and institutions in charge of weights and measures. Historical records show that in the Eastern Han Dynasty, the governor of Jingzhao "leveled quanheng", so "there was no injustice in the market, and the people were satisfied and convinced". The Tang Dynasty set up special supervision and calibration officials. In the Ming Dynasty, quanheng was uniformly supervised and manufactured by the Bao yuan Ju (Bao yuan Bureau) of the Ministry of Works, and the Bingma Si (Military and Horse Bureau) concurrently managed the market bureau, responsible for calibrating weighing instruments. #### 2. The Origin and Evolution of "Quanheng" Both ancient and modern, at home and abroad, the status of the balance remains unshakable. Like ancient Greece and Rome in Europe, China's weighing instruments also first had balances. The ancient balance is basically the same in principle as the modern balance we see in laboratories today, but its appearance is quite different. It has a heng (balance beam) made of wood or bronze. A lifting rope is tied at the midpoint of the beam, and a weighing pan is fixed and hung at each end. One pan holds the object to be weighed, and the other holds the quan (weights). The weights at that time were a complete set of bronze quan of different sizes. The Mohist school, which advocated "what is said must be practiced", recorded the production of quanheng in their work *Mo Jing (Mohist Canon)*: "If weight is added to one side of the heng, it must sag; if the weights are not equal, when balanced, the root (short arm) is short and the tip (long arm) is long. If equal weights are added to both sides, the beam will balance." This text is sufficient to show that as early as the Spring and Autumn and Warring States periods, the Mohist school had an understanding of the lever principle and made quanheng instruments. The Mohist school, which believed in "truth comes from practice". In the middle and late Spring and Autumn Period, the state of Chu had already made small-scale heng instruments—wooden heng and copper ring weights—used to weigh gold coins. A complete set of ring weights has ten pieces, roughly increasing by multiples: 1 zhu, 2 zhu, 3 zhu, 6 zhu, 12 zhu, 1 liang, 2 liang, 4 liang, 8 liang, and 1 jin. Early balances consisted of a beam and two pans. The center of the beam was suspended with a string as the fulcrum, and the pans were suspended from the ends of the beam with strings. There were holes at both ends of the beam, through which the strings were fixed. Since the 1960s, electronic technology has developed amazingly. The combination of the ancient balance and emerging electronic technology has led to the so-called fully electronic balance. The application of balances is still expanding, with an overall trend towards high precision, high efficiency, high anti-interference ability, and the so-called "three highs and three replacements": single-pan balances replacing double-pan balances, electronic balances replacing mechanical balances, and top-loading balances replacing under-loading balances. It can be predicted that more external devices will be combined with balances in the future. Before long, balances, calculators, processors, and printers will be integrated into one. #### The Emergence and Development of Steelyards The basic feature of a balance is that the side of the beam where the weights are hung (power arm) is equal in length to the side where the objects are hung (weight arm). Therefore, the quan (weights) placed should be equal to the weight of the object to be weighed. This makes the balance only suitable for weighing lighter objects. To weigh heavier objects, one would need to place tens or hundreds of kilograms of "quan", which is too troublesome! The wise ancients discovered the principle that "a small weight can balance a thousand catties", and thus the steelyard was born. The National Museum of China houses a bronze heng beam from the Warring States Period. This measuring instrument is neither like a balance nor like the later steelyard, but similar to an unequal-armed balance. After a gradual evolution, the weight arm of the heng beam shortened and the power arm lengthened, becoming the steelyard still in use today. Steelyards can be seen in Tang Dynasty murals in Xinjiang, which had been greatly improved compared with those in the Southern and Northern Dynasties. By the Song Dynasty, large steelyards had appeared, capable of weighing hundreds of catties, installed on a wooden frame so that both buyers and sellers could see clearly. In the Yuan Dynasty mural "Painting of Weighing Fish", a relatively precise "dengzi (small steelyard)" had appeared. Later, the functions of steelyards became more refined, divided into needle scales, hook scales, li deng (steelyard for candareens), fenjin deng (steelyard for gold), pan scales, etc., which could be freely chosen according to the objects to be weighed. The emergence of the steelyard made a significant contribution to the development of weighing technology. During the Tang Dynasty, China's weighing technology was introduced to Japan and other Eastern countries, exerting a positive impact on their weighing technology. ### Summary The measuring instruments of various dynasties in ancient China reflect the wisdom of the Chinese nation and its contributions to world civilization, laying the foundation for the development of modern Chinese metrology. Metrology plays an indispensable role in a country's development and technological progress; they promote each other and jointly create the splendid Chinese civilization. Sources: Guhan Yuan Di, Yishang Wang, Hong Xiaoyan Talks About Ancient and Modern Times