De sphaera mundi is a medieval introduction to the basic elements of astronomy written by Johannes de Sacrobosco c. 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.
A volvelle from a sixteenth-century edition of Sacrobosco's De Sphaera
Picture from a 1550 edition of De sphaera, showing how the curvature of the Earth makes the mast of an approaching ship appear first
A volvelle or wheel chart is a type of slide chart, a paper construction with rotating parts. It is considered an early example of a paper analog computer. Volvelles have been produced to accommodate organization and calculation in many diverse subjects. Early examples of volvelles are found in the pages of astronomy books. They can be traced back to "certain Arabic treatises on humoral medicine" and to the Persian astronomer, Abu Rayhan Biruni, who made important contributions to the development of the volvelle.
A volvella of the moon. A volvella is a moveable device for working out the position of the sun and moon in the zodiac, 15th century
A sixteenth-century wheel chart, a page of Astronomicum Caesareum by Petrus Apianus, 1540, apparently relating to the Moon. The red dragons mark out one odd-sized and 26 equal-sized central divisions; the orbital period of the moon is 27.3 days.
A volvelle from the sixteenth century edition of the De sphaera mundi by Johannes de Sacrobosco.
