 Maaseh Hoshev is sometimes mistakenly referred to as Sefer Hamispar (The Book of Number), which is an earlier and less sophisticated work by Rabbi Abraham ben Meir ibn Ezra (1090–1167).In 1342, Levi wrote "On Sines, Chords and Arcs", which examined trigonometry, in particular proving the sine law for plane triangles and giving five-figure sine tables.One year later, at the request of the bishop of Meaux, he wrote "The Harmony of Numbers" in which he considers a problem of Philippe de Vitry involving so-called "harmonic numbers", which have the form 2"m"·3"n".