Compendium on Using the Device Known as the Almucantar Quarter
This work, by a timekeeper at the Al-Azhar Mosque in Cairo, is an important and comprehensive textbook on timekeeping. It introduces the useful device of dividing a quarter of a circle of projection into sections known as almucantars (muqanṭarāt). The work, comprising 100 folio pages, contains 30 chapters and a conclusion. The work was composed in 1440-1 (844 A.H.) and was copied in 1757 (1170 A.H.).