Cubit

• 1. Introduction

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  A cubit is a unit of length measured from the elbow to the tip of the middle finger, and it once varied so much from place to place that dozens of competing versions coexisted at once, most of them clustering somewhere between about 44 and 53 centimeters, yet none of them agreeing exactly. The Bible mentions the cubit in the story of Noah's Ark, in the dimensions of the Ark of the Covenant and the Tabernacle, and in the account of Solomon's Temple. It was primarily associated with the Sumerians and the Egyptians, yet cubits of different lengths spread across nearly every civilization in antiquity and lasted, in some places, into the 20th century. How did a measurement based on nothing more than a human forearm stay in use for thousands of years across dozens of cultures? Why did the "same" unit end up meaning such different lengths depending on who was measuring? And what happened when rulers, priests, and scholars tried to pin an arm's length down to an exact standard?

• 2. Egypt's Royal Standard

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  The ancient Egyptian royal cubit, known as the meh niswt, stands as the earliest attested standard measure in history. Physical cubit rods were used to take real measurements, and several have survived: two came from the tomb of Maya, the treasurer of the 18th-dynasty pharaoh Tutankhamun, found at Saqqara, and another was recovered from the tomb of Kha at Thebes. In 1865, the scholar Lepsius described and compared fourteen surviving rods, including one double cubit rod, and found them ranging from 523.5 to 529.2 millimeters in length, each divided into seven palms, with every palm further split into four fingers.

  Evidence for the royal cubit's use reaches back to the Early Dynastic Period. On the Palermo Stone, the flood level of the Nile during the reign of the Pharaoh Djer is recorded as measuring 6 cubits and 1 palm. Its use in monumental construction dates back at least as far as the Step Pyramid of Djoser, designed by the architect Imhotep around 2700 BCE.

• 3. Sumer's Many Standards

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  Before any single measure took hold, each city, kingdom, and trade guild in the loosely organized city-states of Early Dynastic Sumer kept its own standard of length. That fragmentation ended, at least officially, when Sargon of Akkad founded the Akkadian Empire and issued a common standard across it. His successor Naram-Sin refined that standard further, though it fell out of use once the Akkadian Empire itself dissolved. It was later revived during the Ur III period through the Nanše Hymn, which narrowed a scattered field of competing measures down to a small set of agreed groupings, a system that the Babylonians, Assyrians, and Persians all went on to adopt from Sumerian civilization.

  In 1916, in the final years of the Ottoman Empire and in the middle of the First World War, the German assyriologist Eckhard Unger uncovered a copper-alloy bar while excavating at Nippur, dating to around 2650 BCE. Unger argued the irregularly marked, irregularly formed rule had served as a measurement standard, and on that basis he calculated the Sumerian cubit at about 518.6 millimeters. Cubits were also pressed into service for measuring the sky: a Babylonian astronomical diary covering 568 to 567 BCE describes Jupiter as one cubit behind the elbow of the constellation Sagittarius, with one cubit reckoned at about 2 degrees of angular separation.

  That Classical Mesopotamian system did not stay confined to Mesopotamia. It became the basis for Elamite, Hebrew, Urartian, Hurrian, Hittite, Ugaritic, Phoenician, Babylonian, Assyrian, Persian, Arabic, and Islamic systems of measurement, and thanks to standardized trade routes, it held a proportional relationship to the Bronze Age metrologies of both Harappan South Asia and Egypt.

  Later Assyrian sculptors worked to at least three distinct standards. Careful measurement of sculpted slabs and figures from Khorsabad, dating to the reign of Sargon II and combined with cuneiform records from the period, points to a standard cubit near 515 millimeters used in ordinary contexts, a "big cubit" of 566 millimeters reserved for depicting religious and mythological beings, and a rarer "cubit of the king" at 550 millimeters used specifically for royal portraiture.

• 4. A Cubit In Scripture

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  By the 2nd century CE, the standard length of the biblical cubit had drifted enough across regions and eras that rabbis felt compelled to pin it down, ruling that the measure they had in mind applied to "the cubit of middle-size." That standard set six handbreadths to a cubit, with each handbreadth equal to four fingerbreadths, a fingerbreadth itself defined as roughly the width of a thumb, about 2.25 centimeters. That math puts a single handbreadth at roughly 9 centimeters and a full cubit, six handbreadths, at about 54 centimeters.

  Epiphanius of Salamis described how the biblical cubit was customarily measured in his own time, in his treatise On Weights and Measures, tracing it from the elbow to the wrist and palm, with the middle finger extended and the span of the hand added below it. Centuries later, rabbinic authorities still disagreed on the exact figure: Rabbi Avraham Chaim Naeh set the cubit at 48 centimeters, while Avrohom Yeshaya Karelitz, known as the Chazon Ish, dissented and set it at 57.6 centimeters instead. The philosopher and rabbi Maimonides, following the Talmud, drew a further distinction between the ordinary six-handbreadth cubit and a shorter, five-handbreadth cubit reserved specifically for measuring the Golden Altar and the base and horns of the altar of burnt offerings.

• 5. Greece, Rome And Islam

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  Ancient Greek units of measurement recognized two forearm-based cubits: a standard forearm cubit, and a shorter "fist" cubit measured from the knuckles of a clenched fist to the elbow. In ancient Rome, Vitruvius described a cubit equal to six palm widths, roughly 444 millimeters, while a separate, longer measure called the Roman ulna ran to about 120 centimeters, close to four feet, taken from the fingers of an arm stretched out to the side opposite the hip.

  The Islamic world inherited the same basic idea, an arm's length from elbow to fingertip, but multiplied it into a wide family of regional standards, each dhirāʿ subdivided into six handsbreadths of four fingerbreadths apiece. The legal cubit, also called the hand cubit or the cubit of Yusuf after the 8th-century judge Abu Yusuf, measured 49.8 centimeters, though it shrank to 48.25 centimeters under the Abbasid Caliphate, possibly as a result of reforms under Caliph al-Ma'mun. The black cubit, fixed by the measure used at the Nilometer on Rawda Island, came to 54.04 centimeters and became the standard across the Maghreb and Islamic Spain. A king's cubit, inherited from the Sassanid Persians, ran to about 66.5 centimeters and was the very measure Ziyad ibn Abihi used to survey Iraq. Cloth cubits varied even more sharply by city: 58.15 centimeters in Egypt, 63 centimeters in Damascus, 67.7 centimeters in Aleppo, and 82.9 centimeters in Baghdad. In Persia, the cubit went by the name gaz, and alongside the standard legal cubit it also took the form of a longer, 79.8-centimeter Isfahan cubit, until a royal gaz-i shāhī of 95 centimeters appeared in the 17th century.

• 6. Countless Local Variants

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  Beyond the handful of major standards, the Islamic world spun off cubits tied to individual trades, cities, and even specific judges. The "small" Hashemite cubit, at 60.05 centimeters, took its alternate name, the cubit of Bilal, from the 8th-century Basran judge Bilal ibn Abi Burda. An Egyptian carpenter's cubit, also called the architect's cubit, was eventually reduced and standardized to exactly 75 centimeters in the 19th century. A house cubit of 50.3 centimeters was introduced by the Abbasid-era judge Ibn Abi Layla, while a cubit of Umar, at 72.8 centimeters, had its own double, a scale cubit established under Caliph al-Ma'mun and used specifically for measuring canals. Cloth merchants in Istanbul, meanwhile, worked to a cubit of 68.6 centimeters, distinct from every other cloth cubit used elsewhere in the region.

• 7. An Arm's Length Endures

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  The measure survived into the 20th century in Persia, where the gaz had by then settled at 104 centimeters, and Mughal India kept its own royal cubit, the dhirāʿ-i pādishāhī, fixed at 81.3 centimeters. Beyond the Middle East and South Asia, forearm-based units turned up under their own local names: the Russian lokot, the Indian hasta, the Thai sok, the Malay hasta, the Tamil muzham, the Telugu moora, the Khmer hat, the Tibetan khru, and the Incan kukuchu tupu, alongside various lengths of ell in northwestern Europe. The Swiss-born French architect Le Corbusier revived the same basic idea in the 20th century with the Modulor, a system of proportion built from human body measurements.

  The unit's oldest sense has never entirely disappeared. In hedgelaying, the length of a person's forearm is still commonly used to judge the interval between stakes set within a hedge. In heraldry, a "cubit arm" depicting a forearm, sometimes shown wearing a sleeve, appears as a charge on coats of arms in various positions, most often standing upright as a crest, as used historically by the families of Poyntz of Iron Acton, Rolle of Stevenstone, and Turton. Even the English word itself carries the anatomy in its root: "cubit" descends from the Latin cubitum, meaning elbow, drawn from the verb cubare, to lie down, the same root that gives English the word "recumbent."