A seated man lifting a weight: equilibrium and the centre of gravity
Statics of a body that holds a load, with painting precepts on matching a figure to its intent
The sheet gathers Leonardo's studies on the equilibrium of a body that lifts or holds a weight, arguing that the weight's centre must fall on the vertical through the point of support and that some counter-weight is always required. A thought-experiment imagines a man sitting with back and legs pressed flat into the angle of a wall, unable to shift his spine yet still moving a weight with his arms, which Leonardo explains by treating the joined arms and trunk as a single iron bent into two right angles. The left column adds a problem on how ten pounds set on a triangle a b c are shared by its base, a note that impact (del colpo) exceeds mere force or weight, and several 'De pittura' precepts on matching a figure to its intent and on placing a lifting figure's legs. Small pen sketches down the right margin show a seated man handling weights.
On this page
The centre of a weight falls on the vertical of its support
The middle of every weight stands on a perpendicular line with the centre of its support. A man, whether standing or seated, who takes up some weight in his arms must have the loaded support lie midway between himself and that weight.
No load carried past the vertical without a counter-weight
It is impossible for the force of the arms, with the weight they hold, to carry it beyond the vertical without an opposing counter-weight. Leonardo answers the objector who imagines himself sitting with back and outstretched legs jammed into the angle of a wall, moving a weight by the arms alone.
Arms and trunk act as an iron bent at two right angles
The force here only makes the arms, united with the trunk, behave as if of a single piece without bending joints. That piece is like an iron bent into two right angles, whose upper end drops on a perpendicular to the middle of its base, so a weight set on the upper end bears straight down upon the base.
Ten pounds on triangle a b c, and the power of the blow
If the weight a weighs ten pounds, how much does each part of the base of triangle a b c feel? A following note 'of the blow' holds that the more the time of the blow is contained within the time of force and weight, the more powerful the blow is than either force or weight.
Make the work resemble the intent
Under 'De pittura': make the work resemble its aim and intention, thinking well who the figure is and what she should be doing. The same action shown by an old man or a youth must appear of greater force the stronger the youth is, and likewise from youth to infant.
Setting a figure's legs to lift a weight
A closing painting note asks, if you must show a man who moves, lifts, pulls or carries a weight like his own, in what manner you should arrange his legs beneath his person. Small marginal figures of a seated man handling weights illustrate the poses.