General rule for bending a heavy body about its pole
The whole weight rests at the base's midpoint; arms a m, r m, t m and infinite division
The verso restates the balance rule with numerical examples. In the upper figure the corner a is the pole and the whole weight of the cube (8 libbre) rests at n; since arm e a is quadruple arm a n, a weight of 2 balances the 8, and the other arms d a, c a, b a are proportioned likewise. The lower figure gives the general rule for bending the heavy body a d q m by a cord fastened at a: all the body's gravity resides at the middle of its base, the pole is corner m, and as the pulling line shortens the arm the balancing power falls, so that by infinite division an infinitely small weight could in the end move the load.
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Corner a as pole; a weight of 2 balances 8
Reckon corner a as the pole and the whole weight of the cube (8 libbre) at point n. Since the arm e a is quadruple to the arm a n, its weight is one quarter, so 2 stands even with 8; the other arms d a, c a, b a are proportioned to a n in the same way.
Gravity at the base's midpoint; infinite division of the arm
To bend the body a d q m by a cord at corner a, all its gravity resides at the middle of its base and the pole is corner m, with the opposite arm m o carrying 4 libbre. As the pulling line shortens the arm (a m quadruple, r m triple, then double, then equal to m o), the balancing power falls, so that by infinite division an infinitely small weight could at last move the load.
Rectangle with fan of lines and a quarter-arc
Each figure is a rectangle with straight lines radiating from one corner and a quarter-circle arc swept across them to a vertex at the right. The intersections of the arc with the cord-lines set the lengths of the balance arms in the proof.