Old men ought to be represented with slow and heavy movements, their legs bent at the knees, when they stand still, and their feet placed parallel and apart; bending low with the head leaning forward, and their arms but little extended.
Women must be represented in modest attitudes, their legs close together, their arms closely folded, their heads inclined and somewhat on one side.
Old women should be represented with eager, swift and furious gestures, like infernal furies; but the action should be more violent in their arms and head than in their legs.
Little children, with lively and contorted movements when sitting, and, when standing still, in shy and timid attitudes.
[Footnote: bracci raccolte. Compare Pl. XXXIII. This drawing, in silver point on yellowish tinted paper, the lights heightened with white, represents two female hands laid together in a lap. Above is a third finished study of a right hand, apparently holding a veil from the head across the bosom. This drawing evidently dates from before 1500 and was very probably done at Florence, perhaps as a preparatory study for some picture. The type of hand with its slender thin forms is more like the style of the Vierge aux Rochers in the Louvre than any later works—as the Mona Lisa for instance.]
Taken from The Notebooks of Leonardo da Vinci edited by Jean Paul Richter, 1880.