Ptolemy and Euclid. 17th century artwork showing Ptolemy (left) and Euclid (right) either side of an astronomical device known as an armillary sphere. The text is in Latin, with the central motto translating as 'the universality of things is like dust in the hand of God'. Ptolemy (2nd century author and astronomer) and Euclid (3rd century BC mathematician) both lived and worked in the Greek culture of Alexandria, Egypt. Euclid is most famous for his Euclidean geometry, and Ptolemy is most famous for his works on astronomy and the natural world. The IAH monogram at bottom is for the 17th century French printer Jean-Antoine Huguetan.