Almagest by Ptolemy
Almagest is the Latin form of the Arabic name (الكتاب المجسطي, al-kitabu-l-mijisti, in English The Great Book) of a mathematical and astronomical treatise proposing the complex motions of the stars and planetary paths, originally written in Greek as Μαθηματικἠ Σύνταξις (Mathematikē Sýntaxis, Mathematical Treatise; later titled Hē Megálē Sýntaxis, The Great Treatise) by Ptolemy of Alexandria, Egypt, written in the 2nd century. Its geocentric model was accepted as correct for more than a thousand years in Islamic and European societies through the Middle Ages and early Renaissance. The Almagest is the most important source of information on ancient Greek astronomy. The Almagest has also been valuable to students of mathematics because it documents the ancient Greek mathematician Hipparchus's work, which has been lost. Hipparchus wrote about trigonometry, but because his works have been lost mathematicians use Ptolemy's book as their source for Hipparchus' works and ancient Greek trigonometry in general.