Binocular vision of a sphere, with balls hung by cords
Why an opaque sphere never looks perfectly round to two eyes; plus a leveling device and a horse-mould note
A faint leaf whose main text argues that an opaque spherical body seen by two eyes never appears perfectly round, and sets out a simple experiment: hold a ball smaller than the gap between the eyes before the face, look at the sky, and observe the effect, which Leonardo explains by the infinite visual lines each eye casts, strongest along the central line. The drawings show balls suspended by cords in triangular rigs, related to a weighing or leveling instrument. A short note concerns the half-mould for casting a horse, and a red-chalk sketch of a standing man occupies the lower right.
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An opaque sphere never looks perfectly round to two eyes
Leonardo asserts that no opaque spherical body seen by two eyes appears perfectly round, and gives an experiment: hold a ball smaller than the interocular distance before the middle of the two open eyes, face the sky, and look at the ball's centre. He explains it by each eye casting infinite visual lines, strongest along the central line.
Balls suspended by cords in triangular rigs
A series of diagrams shows spheres hung from cords in triangular suspensions, apparently a weighing or leveling device. The rigs pair a circle with radiating cords fixed to points below, studying the equilibrium of a hung ball.
Half-mould for the form of the horse
A note beside a framework figure concerns the form (mould) for a horse: for the half-mould that will lie down, Leonardo says it is necessary to test the re-firing while lying down.
Red-chalk sketch of a standing man
A lightly drawn red-chalk figure of a standing man, seen roughly from behind or the side, occupies the lower right of the sheet, unconnected to the geometrical and optical notes.