Three spheres and a cube with its octuple
Solids of varying size with the squares 25 and 9 in red chalk
In red chalk the sheet shows three spheres of different diameters and, below them, a cube drawn in perspective and ruled into a three-by-three grid beside a single small square. The caption names them a cube face and an 'octuple cube', that is a cube of eight times the volume. At the upper left stand the numbers 25 and 9.
On this page
A cube face and its octuple; three spheres
A single small square stands for the face of a unit cube, while the larger gridded cube is its 'octuple' - a cube of double edge and eightfold volume. Three spheres of graded diameter accompany them.
The numbers 25 and 9
At the upper left Leonardo writes 25 above 9 in red chalk. The pair sits with the study of proportions among the solids on the sheet.