In 1991, Christie’s auction house received a precious object that attracted attention not only because of its beauty, but also because of the mysterious symbols carved into its surface. The instrument was a medieval astrolabe, which our ancestors used for astronomical calculations. It was probably made in Spain in the late 14th century, and it is highly likely that it changed hands many times.
Among the experts interested in it was the British historian David A. King, who saw similar markings in a manuscript from Normandy, in northern France, dated around the same time. They were numerical notations unknown even to specialists in medieval studies and the history of mathematics. Invented by Cistercian monks in the late 13th century, it was a method of writing numbers used in monasteries across Europe for at least two centuries. At that time, Arabic numerals were beginning to be used more than the Roman version, but it would be centuries before the new system was widely accepted.
The Cistercians do not seem to have contributed to this dispute in any way: their notation was actually more of a third alternative, useful to European monks from England to Italy, from Spain to Sweden. And it enjoyed a certain popularity, because, unlike Roman numerals, it provided the possibility of writing any number with only one symbol. However, like the Roman system, that Cistercian system was not easy to multiply or divide.
By the time the printed book had already replaced manuscripts as a means of transmitting knowledge, 0, 1, 2, 3, 4, 5, 6, 7, 8 and 9 had already conquered the world. Roman I, V, X, L, C, D and M have reserved their place in history. But the Cistercian numbers were rejected to such an extent that only a century later they had already become a mystery. One exception, King points out, was the use of this numbering until the 18th century to mark the numbers on wine barrels and measuring rod scales in Flanders.
Cistercian numerals have surfaced only a few times in history, most prominently when they were adopted by Freemasons in Paris in 1780, and in nationalist writings on German folklore from the 20th century.
But how did the system – which the German Renaissance mathematician Agrippa of Nettesheim described as “very elegant numbers” – actually work?
“Very elegant numbers”
According to King, the system of the Cistercian monks was based on a simple notation representing the numbers 1 to 99, which was brought to England from Athens by the monk John of Basingstoke in the early 13th century.
Over time, the system was expanded to represent every number from 1 to 9,999 with a single digit. In his famous book Chronicle of Majors, the Benedictine monk and historian Matteo de Paris taught how to write them. In the figure below, each corner, or quadrant, contains a symbol for thousands (1), hundreds (2), tens (3), and units (4), in the following order: As it spread through the Cistercian monasteries, this system underwent slight modifications depending on the language the monks spoke.
At one point, the baseline was horizontal, but by the 14th century, French monks had returned it to its original position. Matteo de Paris pointed out that “the most fascinating thing and what we do not find in the case of Roman or Arabic numerals is that each number can be represented by a single character”. The problem, of course, is being able to read and write with the help of this system. But if you follow the basic rules, it will not be as difficult as it seems at first glance.
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