“Thirty days hath September…” A Very Rare 16th c. Compotus

COMPUTING. MNEMONICS. CALENDRICS. Anianus, Magister (mid 13th c.)

Compotus manualis Magistri Aniani cum familiarissimo Iacobi Marsi Delphinatis commentario, cu(m)q(ue) Magistri Nicolai Bonespei Kale(n)dario, & Cerei paschalis tabula, & aliisq(ue) multis pro ipsius noticia conducibilibus, nuper editus.

Paris: No printer, 1544

$8,500.00

Small octavo: 13.1 x 8.6 cm. [176] unnumbered p. Collation: A-L8

A VERY RARE PARISIAN EDITION. (The first ed. was printed at Paris in 1483).

Illustrated with numerous woodcuts of computing hands, and two diagrams for calculating the golden number and Dominical letters. Bound in 17th c. mottled French calf, ruled in blind, restoration to spine and board edges. Contents fine though cropped a bit close, occ. shaving the outer margin of the woodcuts.

Illustrated with numerous woodcuts of computing hands, and two diagrams for calculating the golden number and Dominical letters. Bound in 17th c. mottled French calf, ruled in blind, restoration to spine and board edges. Contents fine though cropped a bit close, occ. shaving the outer margin of the woodcuts.

A mid-16th c. edition of the first printed computus (the first edition was printed at Paris in 1483.) “It is one of the best examples of the mediaeval computus that appeared in print. Unlike the first edition it contains a number of illustrations showing the use of the hand and fingers in assisting in calendar reckoning, the title of ‘Computus manualis', being thus justified.”(Smith p. 33 – 34)

It is the source of perhaps the most famous of rhyming calendrical mnemonics, “Thirty days hath September…”.

Junius Aprilis September et ipse November
Dant triginta dies reliquis supadditur unus
De quorum numero Februarius excipiatur.

“A computus (compotus) is a work concerned with calculation of the church calendar and contains the rules for computing the date for Easter. In the “western” churches, Easter is the first Sunday after the first full moon after the spring equinox. Knowing the date for Easter for any given year, it is then possible to determine the dates for all the other movable Christian festivals. This calendar problem, essentially coordination of the solar with the lunar year, is of great consequence in the history of calculation in Europe, for it kept the study of mathematics alive during the so-called Dark Ages. 

“Most computus works tend to be prolix, obtuse and complex (see, for example, Schönborn; Computus, 1567, or Arnald of Villanova; Computus, 1501). In contrast, the Anianus computus is written in verse (including the first printed Latin version of the verse Thirty days hath September ...). The Anianus computations themselves are not algorithmic but are based on the use of the fingers and joints of the left hand as both a mnemonic aid and calculating device. The large number of incunable editions attests to the utility and popularity of this approachable work.

“Little is definitively known of Magister (master or teacher) Anianus; however, it is likely he was a French monk who lived in the second half of the thirteenth century at the Benedictine monastery of Aniane near Montpellier.” (Tomash)

Edited by Jacques Marse with a calendar by Nicolas Dupuy (also known in Latin as Nicolaus Bonaspes), an early 16th-century French scholar from Troyes (in Champagne region) who taught humanities at the College de Navarre and at the College de Bayeux.

For a succinct discussion of this method of computation, see Sachiko Kusukawa, A manual computer for reckoning time. In Claire Richter Sherman, Writing on hands. Memory and knowledge in early modern Europe. Seattle, 2000, pp. 28–34. For an earlier discussion of this work, see David Eugene Smith; Le comput manuel de Magister Anianus, 1928

Brunet II, 208. See Honeyman I, 97-98; Pettegree, French Books, 53366