A Treatise on Painting, by Leonardo da Vinci
Senex and Taylor, London
When you understand Perspective and Anatomy well, and have a tolerable Notion of the Parts and Members of Bodies, take all Occasions of observing the different Attitudes and Gestures of Men, in different Actions. For Example, in your Walks, when the Mind is free and disingaged, observe the Motion of those about you; whether they be conversing familiarly together, disputing one among another, quarreling, or even coming to Blows: Observe the Behaviour of those about them, whether they be indeavouring to separate them, or amusing themselves with the sight of the Scuffle; and whatever you remark in this kind, Design upon the Spot. For this Purpose, it will be convenient to have a Pocket-Book always about you, the Leaves of which may be fasten'd in such manner, as to take out without Tearing. For these are things that you cannot preserve with two much Care; the Memory it self being far unequal to that Infinity of Objects, which present themselves to a Painter, aud which he may find Occasion to make Use of, in his future Performances.