Cost calculations for a round fortress tower
A working page of arithmetic costing a tower 20 braccia high and 25 thick, halved for its internal voids
This verso is a working sheet almost wholly filled with columns of multiplication and division, worked in ink over a reddish stain that spreads across the upper calculations. The one passage of prose costs a round tower 20 braccia high and 25 thick at 575 canne, or 575 ducats if built entirely solid, from which Leonardo knocks off half to allow for an interior wall, the defensive passages and other voids. Two small ringed diagrams at the head carry the figures 44 and 14. The rest of the page is given over to trial sums, several partly overwriting one another.
On this page
Cost of a solid round tower, halved for its voids
A tower 20 braccia high and 25 thick is reckoned at 575 canne, so that to make it entirely solid comes to 575 ducats. Leonardo then knocks off half, allowing for an interior wall, the passages of the defenses and other voids.
Columns of trial multiplication and division
Most of the sheet is taken up with tabulated arithmetic, including a 22 by 7 product giving 154 and repeated divisions such as 3850 over 275 giving 14. Several of the working columns overlap and are half-covered by later sums.
Tower reckoned in canne and ducats
The costing equates canne of masonry directly with ducats, one ducat to the canna, before halving the total to account for the tower's hollow parts.