'A lathe. Down below, in this very house. Imagine my parents' consternation. They had taught me Latin, Greek, French, and other languages. They had taught me the lute, the viol, and the harpsichord. Of literature and history I had learned everything that was in their power to teach me. Mathematics and philosophy I learned from Descartes himself. But I built myself a lathe. Later I taught myself how to grind lenses. My parents feared that they had spawned a tradesman.'