Royal cubit

This cubit measure from Abd al-wadide was discovered in a section of wall on the Qaysariyya of Tlemcen[1]. It is rectangular in shape and carries a sculpted inscription in Andalusian characters on one side, spread over two cartouches.

A working system of weights and measures is essential for the economic functioning of any civilisation. Indeed, commonly agreed-upon units of length, surface, volume and weight are necessary in all commercial transactions (whether for exchange, buying or selling), in remuneration for work, in construction and canalisation projects or for the parcelling out of lands and tax collection.

The oldest units of measure appeared with the emergence of writing in the 4th millennium. They were based on parts of the human body (the elbow, the fingers…) or on the quantity of work carried out in a given time (estimations of long distances in terms of days of labour). Eventually these ‘natural’ measures were standardised and acquired more or less fixed values (for a particular group during a precise period, but nevertheless susceptible to considerable variations depending on the region or period). These variations could affect not only the absolute value of a unit of measure (in relation to our current system), but also their relative values.

Legally speaking, a cubit was four palm widths of the hand (index, major, ring finger, little finger side by side) each equal to six digits, a digit being the equivalent of six grains of barley set in line. The number of cubits in use in the world of Islam was considerable. It can be broken down into roughly four measures: the common cubit, the black cubit, the royal cubit and the cubit for fabric. The starting point of all evaluations is the cubit of the Nilometer of Rawda Island (861) in Cairo, which is equivalent to approximately 54.04 cm.

The legal cubit[2] measures 49.8 cm. During the Abbasidian era, in Baghdad, its length was slightly less, about 48.25 cm, going back perhaps to al-Ma’mûn[3], the author of a reform of measures. The royal cubit, which originated in Persia, known since the ’al-Mansûr era[4] as the (large) Hashimit cubit, consisted of eight kaddas instead of six and measured on average 66.5 cm. It was identical to the Ziyâdite cubit that Ziyâd ibn Abihî (m. 673) used in the rebuilding of Iraq and which came to be called, for this reason, the surveying cubit. The black cubit was fixed at 54.04 cm and is identical to the standard cubit in use in the Maghreb and Spain. It was introduced under the Abbasidians but not, as it is assumed, under al-Ma’mûn who used the legal cubit. The cubit of Tlemcen can be compared to the black cubit; although it is slightly shorter. The textile cubit, known in trading in the Levant under the name of ‘pic’, varied from city to city.

This cubit, which is from the Abd al-wadide period is identical to the black cubit, but its length was slightly shorter, about 47 cm, a measurement particular to the qaysariyya of Tlemcen. Brosselard has qualified this cubit as ‘royal’ because he considers it to be contemporaneous with the Abd al-wadide prince Abû Tâshufîn Ist, a creative and innovative leader. This cubit was used as a basic unit for all measures of length.

[2] It is the same as the Egyptian palm cubit, the cubit of Joseph (a name derived from qadi Abû Yûsuf, who died in 798), to the cubit of the post, the free cubit and the cubit of spun wool.

[3] Abbasid caliph that reigned from 786-833.

[4] Abbasid caliph that reigned from 754-775.