A recently cataloged 16th century astronomy book provides fascinating insight into how a particular kind of diagram was printed and constructed. These rotating diagrams, called volvelles (from the Latin volvere, to turn), were used in both manuscripts and printed books to calculate data related to calendars, tide tables, astronomy, astrology, and more. They typically consist of one or more circles surmounted by other graduated or figured circles or pointers which rotate from a central axis. The circles could be made of paper, cardboard, or vellum, and the pivots were typically made of string or thread. The most common were printed with woodcuts.