Time was when readers kept commonplace books. Whenever they came across a pithy passage, they copied it into a notebook under an appropriate heading, adding observations made in the course of daily life. Erasmus instructed them how to do it.
… They broke texts into fragments and assembled them into new patterns by transcribing them in different sections of their notebooks. Then they reread the copies and rearranged the patterns while adding more excerpts. Reading and writing were therefore inseparable activities. They belonged to a continuous effort to make sense of things, for the world was full of signs: you could read your way through it; and by keeping an account of your readings, you made a book of your own, one stamped with your personality."