Land-yield reckoning, abacus problems and bridge sketches
A square-mile grain calculation in ducats, fraction exercises, a geared cart, and movable bridges
The verso mixes calculation with the movable-bridge drawings that show through from the recto. A long worked example on the left computes how much grain a square mile of sown land yields and converts it into lire and gold ducats, ending with the owner's share after the labourer is paid. Below, an abacus (abbaco) lesson works fraction problems such as one third of a quarter; at the centre a small cart with two toothed wheels is labelled 400 – 400, and trussed and arched bridges are lightly drawn across the sheet.
On this page
How much grain a square mile of sown land yields
Taking a square mile as 3000 braccia per side and a square staioro as 40 braccia per side, the note finds the staioro fits 75 times along the side and 5625 times over the area, giving 1875 seed-staiora. At 20 staia harvested per staio sown, 20 soldi the staio, this comes to 37500 lire, that is 5357 1/7 gold ducats; half going to the labourer leaves the owner 2678 ducats and 4 lire.
Abacus lesson: taking a fraction of a fraction
The abbaco block teaches how to take one fraction of another: for 1/3 of a quarter, multiply 3 by 4 to get 12, so the answer is 1/12; for 1/5 of a sixth, 5 times 6 is 30, giving 1/30; and for 2/3 of 3/4, multiplying the denominators gives 12, of which 3/4 is 9 and 2/3 of 9 is 6.
Cart with two toothed wheels
A small figure of a cart carried on two toothed (geared) wheels is annotated 400 – 400, apparently giving a count or dimension for each wheel. It sits among the calculations at the centre of the sheet.
Movable bridges showing through
A trussed span across the upper sheet and a lightly drawn arched bridge in the centre echo the movable-bridge designs of the recto, drawn faintly among the columns of figures.