About “De sphaera mundi”
De sphaera mundi is a medieval introduction to the basic elements of astronomy written by Johannes de Sacrobosco around 1230. Based heavily on Ptolemy's Almagest and drawing additional ideas from Islamic astronomy, it was one of the most influential works of pre-Copernican astronomy in Europe. (Summary adapted from Wikipedia, CC BY-SA 4.0.)
Some summaries adapted from Wikipedia, CC BY-SA 4.0.