Diminution of figures and solids along a beam of rays
Trapezoids, a rectangle divided into twenty-fourths, and cylinders set within converging rays
On blue prepared paper Leonardo lays out geometric figures within converging beams of rays: small trapezoids and triangles (each marked a), a long rectangular solid and cylinders whose lines run to a distant point, and a compass rose or star at upper right. A rectangle set inside a sheaf of rays is graduated with the fractions 6/24, 8/24, 12/24 up to a whole 24, marking how a magnitude is divided along the beam. The solids are lettered, the cylinder carrying the sequence m l, K c b a, f e d, h g. The labels alone are transcribed; the sheet carries further faint construction lines and untranscribed notes.
On this page
Trapezoids, triangles and a lettered cylinder
Rows of small trapezoids and triangles are each marked with the letter a, and a cylinder is annotated with the letters m l, K c b a, f e d and h g. These solids sit within long converging lines that run to a vanishing point at the right. They form the geometric bodies whose apparent size is being studied along the rays.
A rectangle graduated in twenty-fourths within a beam of rays
A rectangle placed inside a sheaf of rays is divided by the fractions 6/24, 8/24 and 12/24 up to the full 24. The numbers scale a single magnitude at successive stations along the converging beam. The figure ties the arithmetic of the fractions to the optical diminution of the rays.