Toby Lester - Da Vinci's Ghost

APA: Lester, T (2012). Da Vinci's Ghost: Genius, Obsession, and How Leonardo Created the World in His Own Image. Free Press.

pages 117-118:

Leonardo didn't just model his notebooks on the sketchbooks of artists and engineers. He also turned to another source for inspiration: the commonplace book, designed to preserve not pictures, but words.
Students receiving a formal education in Leonardo's day were taught from a very early age to keep commonplace books -- notebooks, that is, in which they collected excerpts from their reading, organized not by author or book but by subject. Central to the pedagogy of the age, the commonplace book has two main functions. It helped students develop educationally desirable habits of mind, based on the categories their teachers had them divide their notebooks up into, and it allowed them to organize a store of the best that had been thought and said.
... A how-to-guide for the keeping of a commonplace book survives from the early 1500s. "Make a book of blank leaves of a proper size," it reads. "Divide it into certain topics -- so to say, into nests. In one, jot down the names of daily converse: the mind, body, our occupations, games, clothes, divisions of time, dwellings, foods; in another, idioms or formulae docendi; in another, sententiae; in another, proverbs; in another, difficult passages from authors; in another, matters which seem worthy of not to you or your teacher."
The instructions were modern, but the practice had ancient roots. Writing in the first century, Seneca had described it in a manner that would have appealed very much to Leonardo. "We should imitate bees," he wrote, using an analogy much cited during the Middle Ages and the Renaissance, "and keep in separated compartments whatever we have collected from our diverse reading, for things conserved separately keep better. Then, diligently applying all the resources of our native talent, we should mingle all the various nectars we have tasted and turn them into a single sweet substance, in such a way that, even if it is apparent where it originated, it appears quite different from what it was in its original state."