Early units and standards
Ancient Mediterranean Systems
Body measurements probably provided the most convenient bases for early linear measurements; early weight units may have derived casually from the use of certain containers or from calculations of what a person or animal could lift or haul. The historical progression of units has followed a generally westward direction, the units of the ancient empires of the Middle East finding their way, mostly as a result of trade, to the Greek and then the Roman empires, thence to Gaul and Britain via Roman conquest.
Although there is evidence that many early civilizations devised standards of measurement and some tools for measuring, the Egyptian cubit is generally recognized as having been the most ubiquitous standard of linear measurement in the very ancient world. Developed about 3000 BC, it was based on the length of the arm from the elbow to the extended fingertips and was standardized by a royal master cubit of black granite, against which all the cubit sticks in use in Egypt were measured at regular intervals.
The royal cubit (524 millimetres, or 20.62 inches) was subdivided in an extraordinarily complicated way. The basic subunit was the digit, doubtlessly a finger's breadth, of which there were 28 in the royal cubit. Four digits equaled a palm, five a hand. Twelve digits, or three palms, equaled a small span. Fourteen digits, or one-half a cubit, equaled a large span. Sixteen digits, or four palms, made one t'ser. Twenty-four digits, or six palms, were a small cubit. The digit was in turn subdivided. The 14th digit on a cubit stick was marked off into 16 equal parts. The next digit was divided into 15 parts, and so on, to the 28th digit, which was divided into 2 equal parts. Thus, measurement could be made to digit fractions with any denominator from 2 through 16. The smallest division, 1/16 of a digit, was equal to 1/448 part of a royal cubit.
The accuracy of the cubit stick is attested by the dimensions of the Great Pyramid of Giza; although thousands were employed in building it, its sides vary no more than 0.05 percent from the mean length of 230.364 metres (9,069.45 inches).
The Egyptians developed methods and instruments for measuring land at a very early date. The annual flood of the Nile River created a need for benchmarks and surveying techniques so that property boundaries could be readily reestablished when the water receded. The Egyptian weight system appears to have been founded on a unit called the kite, with a decimal ratio, 10 kites equaling 1 deben, and 10 debens equaling 1 sep. Over the long span of Egyptian history, the weight of the kite varied from period to period, ranging all the way from 4.5 to 29.9 grams (0.16 to 1.05 ounce). About 3,400 different weights have been recovered from ancient Egypt, some in basic geometric shapes, others in human and animal forms.
Egyptian liquid measures, from large to small, were ro, hin, hekat, khar, and cubic cubit (0.14 cubic metre [37 U.S. gallons]).
The earliest of all known weights is possibly the Babylonian mina, which in one surviving form weighed about 640 grams (23 ounces) and in another about 978 grams (34 ounces). Archaeologists have also found weights of 5 minas, in the shape of a duck, and a 30-mina weight in the form of a swan. The shekel, familiar from the Bible as a standard Hebrew coin and weight, was originally Babylonian. Most of the Babylonian weights and measures, carried in commerce throughout the Middle East, were gradually adopted by other countries. The basic Babylonian unit of length was the kus (about 530 millimetres, or 20.9 inches), also called the Babylonian cubit. The Babylonian shusi, defined as 1/30 kus, was equal to 17.5 millimetres (0.69 inch). The Babylonian foot was 2/3 kus.
The Babylonian liquid measure, ka, was the volume of a cube of one handbreadth (99 to 102 millimetres, or 3.9 to 4 inches). The cube, however, had to contain a weight of one great mina of water. The ka was a subdivision of two other units; 300 ka equaled 60 gin and 1 gur. The gur represented a volume of almost 303 litres (80 U.S. gallons).
The Hittites, Assyrians, Phoenicians, and Hebrews
derived their systems generally from the Babylonians and Egyptians. Hebrew standards were based on the relationship between the mina, the talent (the basic unit), and the shekel. The sacred mina was equal to 60 shekels, and the sacred talent to 3,000 shekels, or 50 sacred minas. The Talmudic mina equaled 25 shekels; the Talmudic talent equaled 1,500 shekels, or 60 Talmudic minas. The volumes of the several Hebrew standards of liquid measure are not definitely known; the bat may have contained about 37 litres (nearly 10 U.S. gallons); if so, the log equaled slightly more than 0.5 litre (0.13 U.S. gallon), and the hin slightly more than 6 litres (1.6 U.S. gallons). The Hebrew system was notable for the close relationship between dry and liquid volumetric measures; the liquid kor was the same size as the dry homer, and the liquid bat corresponded to the dry 'efa.