Maestro Benedetto da Firenze (1429-1479), a pupil of Calandro di Piero Calandri, taught privately in the abacus schools. Leonardo (who as a boy had been enrolled in such a school) remembers him in a list of people to meet around 1478: “Benedetto de l’abbacho” (Codex Atlanticus, f. 42v). The Trattato, composed in 1465, is an example of Benedetto’s teaching. The Codex Laurentianus, datable to around 1480, was written in the same environment by Pier Maria di Calandro Calandri.