If you’re looking to enrich your fantasy or Medieval fiction, why not mention Cistercian numbers — the forgotten ciphers of Medieval monks? As Tibi Puiu reports on ZME Science, people have employed all sorts of systems throughout history, most of which are now forgotten. These include the intriguing Cistercian numbers used by monks in the Middle Ages, but also by Nazis and occultists in the 20th century.

Various Cistercian numbers from 1 to 9999 can be represented by superimposing up to 36 basic forms. Source: ZME Science

A Simple Logic

While Cistercian numbers may look odd at first, they are simple to use once you grasp the logic behind them. Numbers are represented by nine appendages to vertical stems that each correspond to units, tens, hundreds, and thousands.

Cistercian numbers are represented on a quadrant using horizontal and vertical staves. Source: ZME Science

Each of the four different orientations (1-9, 10-99, 100-999, 1000-9999) can be represented by changing the coordinates. So, practically, changing the coordinate of each ligature — either by rotating or mirroring them — can alter the digit from being a unit to a thousand. When the appendages are combined on a single stem, you get a cipher representing any number from 1 to 9999.

Changing the coordinate of each ligature can alter the type of digit. Source: ZME Science

A 13th-Century Invention

This peculiar number-notation was invented in the late 13th century by Cistercian monks, near the border region between France and Belgium. For two centuries, the number system was used by monks belonging to the order across all of Europe as an alternative to the well-known Roman numerals and the ‘novel’ Hindu-Arabic numerals, the latter of which were just beginning to get adopted at the time.

The monks used this system to represent year-numbers in dates, and to number staves of music and pages of manuscripts. However, it also proved useful outside of the monasteries. We know the numerical notation was used in astronomy because Cistercian numerals were etched on astrolabes — a handheld medieval astronomical instrument — and used for astronomical tables compiled in Salamanca in the late 15th century.

The system eventually fell out of grace in favor of the much more flexible Hindu-Arabic numbering system, in part because Cistercian numbers are useful for representing only compact numbers up to 9999, as well as due to the fact that they were challenging to print. However, Cistercian ciphers would survive in use as secret codes. The Freemasons in Paris adopted it in 1780, and occultists and Nazis re-discovered the Cistercian numeral system in the early 20th century.

If you wish to have fun with Cistercian numbers, this website has a nifty online tool that converts Arabic numbers into them.