This manuscript is one of the three surviving 16th-century copies of the astronomical theories of Ptolemy (100−168 CE). This compendium of ancient science, founded on observation of the heavenly bodies, calculation and measurement, comprises 55 diagrams, 11 of which are removable. Forgotten in the Middle Ages, Ptolemy’s work was rediscovered by the Arab-Muslim world. Contrary to the concurrent theories of medieval Europe, the astronomer of the 2nd century saw the Earth as a round planet and assumed that it was possible to travel all the way round it.