In the previous chapter, we have seen how geometry problems are illustrated in libri d’abbaco. In this chapter, I explore how diagrams constructed using simple geometrical figures served to demonstrate the mechanisms of the cosmos as described in the poem the Sfera by Goro Dati. As mentioned in the previous chapter, a knowledge of geometry was essential to many occupations, including those of artists and merchants. But the art of geometry had uses for more elevated subjects: as we learn in Quintilian’s Institutio oratoria, ‘geometry soars still higher to the consideration of the system of the universe’. Capturing celestial bodies in geometrical figures was the only known method for exploring their physical laws.