祖冲之
Any horizontal cross-section of a cloister vault is a square. This fact may be used to find the volume of the vault using Cavalieri's principle. Finding the volume in this way is often an exercise for first-year calculus students, and was solved long ago by Archimedes in Greece, Zu Chongzhi in China, and Piero della Francesca in Renaissance Italy; for more, see Steinmetz solid.