Because Florence’s guild of notaries barred those who were non legittimo, Leonardo was able to benefit from the note-taking instincts that were ingrained in his family heritage while being free to pursue his own creative passions. This was fortunate. He would have made a poor notary: he got bored and distracted too easily, especially when a project

His mechanical engineering work included close to a hundred devices for moving and diverting water.

The Italian Renaissance was producing artist-engineer-architects who straddled disciplines, in the tradition of Brunelleschi and Alberti, and the tiburio project gave Leonardo the opportunity to work with two of the best: Donato Bramante and Francesco di Giorgio. They became his close friends, and their collaboration produced some interesting

Leonardo was not always a giant. He made mistakes. He went off on tangents, literally, pursuing math problems that became time-sucking diversions. Notoriously, he left many of his paintings unfinished, most notably the Adoration of the Magi, Saint Jerome in the Wilderness, and the Battle of Anghiari. As a result, there exist now at most fifteen

Botticelli, whose workshop turned out devotional Madonnas at a faster clip than even Verrocchio’s, was seven years older than Leonardo and had won far greater patronage from the Medici. He was good at courting such favor.

What made Vitruvius’s work appealing to Leonardo and Francesco was that it gave concrete expression to an analogy that went back to Plato and the ancients, one that had become a defining metaphor of Renaissance humanism: the relationship between the microcosm of man and the macrocosm of the earth. This analogy was a foundation for the treatise that

The utopian city he envisioned would have two levels: an upper level designed for beauty and pedestrian life, and a level hidden below for canals, commerce, sanitation, and sewage.

Along the way, he and his traveling party stopped in Milan. Salai decided to stay there, at least temporarily. He was then thirty-six, solidly middle-aged and no longer playing the role of Leonardo’s pretty-boy companion or competing for attention with the aristocratic Melzi, who was still only twenty-five and remained at Leonardo’s side. Salai

Make lists. And be sure to put odd things on them. Leonardo’s to-do lists may have been the greatest testaments to pure…

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