Above: The harmony of the spheres; Below: The planetary orbits — "The idea of the harmony of spheres – that numerical proportions corresponding to musical harmonies governed both the movement of the seven heavenly bodies and their distance from the Earth – was taken up by medieval writers from ancient thought. In the illustration of the harmony of the spheres in the upper part of the page, the Sun, the Moon, and the five known planets are depicted as seven discs of equal size. Between them are written musical intervals -- a tone (tonus), a semitone (semitonium), or three semitones (tria semitonia). The diagram below shows the Earth at center. The names of the zodiac are written in the outer frame. The names of the planetary bodies are written above their orbits, shown as red rings. Because each of these heavenly bodies has its own, eccentric orbit, the rings representing their orbits are not concentric."

Featured on PDR in the collection Cosmography Manuscript (12th Century)

This wonderful series of medieval cosmographic diagrams and schemas are sourced from a late 12th-century manuscript created in England. Coming to only nine folios, the manuscript is essentially a scientific textbook for monks, bringing together cosmographical knowledge from a range of early Christian writers such as Bede and Isodere, who themselves based their ideas on such classical sources as Pliny the Elder, though adapting them for their new Christian context. As for the intriguing diagrams themselves, The Walters Art Museum, which holds the manuscript and offers up excellent commentary on its contents, provides the following description: