Woodcut engraving. A volvelle was used for finding the position of the moon in the zodiac, given the position of the sun and the age of the moon. There is an engraved circle with 31 divisions, into which a separate piece of paper is attached with a red satin ribbon. This inner piece is marked with signs of the Zodiac, and rotates around the circle. An extremely interesting apparatus, more amazing for the fact that is still fully functional.