Best known for his 1906 discovery of lost texts in the Archimedes Palimpsest, Danish scholar Johan Ludvig Heiberg (1854–1928), professor of classical philology at Copenhagen, published numerous editions of ancient mathematicians, including Archimedes and Apollonius of Perga (also reissued in this series). Between 1898 and 1907, he published in three parts the extant astronomical works of Ptolemy, active in second-century Alexandria. The Ptolemaic system, his geocentric model of the universe, prevailed in the Islamic world and in medieval Europe until the time of Copernicus. This first part of Volume 1, published in 1898, contains a brief Latin preface and the Greek text of Books 1-6 of Ptolemy's major astronomical treatise, known as the Almagest. It demonstrates how to use astronomical observations to construct cosmological models and includes tables that make it possible for celestial phenomena to be calculated for arbitrary dates.