If you believe that the Moon’s activity affects the human body, as this medieval manuscript describes, then a lunar volvelle is a particularly useful device. The revolving discs may be rotated to calculate the position of the Moon in relation to that of the Sun. As the top disk is turned, the outer circular window reveals the changing phases of a shining, golden Moon. The colourful gentleman is known as a Zodiac Man and illustrates how each body part is related to a zodiac sign. The accompanying text warns physicians against operating on a body part when the Moon is in its associated sign.
(England, after 1387)
Click here to see more medieval examples of the Zodiac Man.
The video below explains the different parts of the volvelle, one of the ways in which it would have been used in the Middle Ages, and calculates the position of the moon for the 50th anniversary of the moon landing.