Chapter LXV

When you have thoroughly learnt perspective, and have fixed in your memory all the various parts and forms of things, you should often amuse yourself when you take a walk for recreation, in watching and taking note of the attitudes and actions of men as they talk and dispute, or laugh or come to blows one with another, both their actions and those of the bystanders who either intervene or stand looking on at these things; noting these down with rapid strokes in this way, in a little pocket-book, which you ought always to carry with you. And let this be of tinted paper, so that it may not be rubbed out; but you should change the old for a new one, for these are not things to be rubbed out but preserved with the utmost diligence; for there is such an infinite number of forms and actions of things that the memory is incapable of preserving them, and therefore you should keep those (sketches) as your patterns and teachers.

_Leonardo._