BONFILS, IMMANUEL

Kanfei Nesharim [“Wings of Eagles.”]
Manuscript in Hebrew, written in a cursive Italian hand, on paper. With astronomical tables forecasting solar and lunar positions.
ff. (24). Stained, tears to outer edges crudely repaired all unaffecting text. Modern calf-backed boards. 4to.
Senigallia, (Province of Ancona, Italy): 1478
UNPUBLISHED MANUSCRIPT. A medieval composition on astronomy also referred to as Sheish Kenafayim (“Six Wings.”) Divided into six parts, the manuscript begins with an introduction, followed by charts and calculations. A colophon is present on p. 23a: “I, Pinchas Tzvi have copied this from a foreign language into the Holy Tongue, here in Senigallia [5]238 (1478).” Pinchas Tzvi’s signature is found in other medieval manuscripts where he signs his full name: “Pinchas Tzvi son of Nathaniel Davison who is called ibn Turin, a student of the doctors of Senigallia” (see Jewish Historical Institute, Warsaw ms. 253). Immanuel ben Jacob Bonfils (c. 1300-1377) was a French mathematician and astronomer, a pioneer of exponential calculus, credited with inventing the system of decimal fractions. Bonfils studied the works of Gersonides (Levi ben Gershom), the father of modern trigonometry, and subsequently taught at the academy founded by Gersonides in Orange, Provence. While living in Tarascon, Bonfils composed in 1365 the work for which he would become best known: Sepher Shesh Kenafayim, or Kanfei Nesharim as it is called in the present manuscript. A text on eclipses that featured astronomical tables, it also includes data for every important date in the Jewish calendar, along with correction factors necessary for locations further afield. His work was translated from Hebrew into Latin in 1406 and into Greek in 1435. Bonfils' calculations were extensively used by sailors and explorers until well into the 17th century.