The Angel of the Ninth Sphere, or Primum Mobile, plate 49 from Planets and Spheres

The Ferrara nobility used these enigmatic flash cards, whose engraver’s identity is now unknown, to tutor their children in the structure of the world and the greater cosmos. With images ranging from a human beggar to God himself, the fifty cards in each set were divided into five groups: Ranks and Conditions of Men, Apollo and the Muses, Arts and Sciences, Genii and Virtues, and Planets and Spheres. The stationary angel with the starry disc in plate 48 represents the firmament as a fixed pattern of stars, which according to Ptolemaic thought revolved around the earth. Plate 49 presents the invisible outer sphere as an empty disc held by a dancing angel.