How much faster the larger weight descends
Spheres m, n and cubes p, q test the speed of fall against air resistance
A problem in comparative fall opens the folio: two spheres, m marked 8 and n marked 1, and two cubes, p divided into eight small cubes the size of q, test how much faster a body of twice the diameter descends. Leonardo argues that although p is eight times q it falls only about twice as fast, then works a numerical example in which q is three pounds and the air resists by one pound. Reducing the weights against the air's resistance, he concludes that the larger body proves "ten times faster," weighing volume, weight, and air resistance together.
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Twice the diameter does not mean eightfold speed of descent
Of two figures, one has twice the diameter of the other, and Leonardo asks how much faster it will descend. Although p is eight times q by bulk, it is no faster in descent than about twice q. The spheres m and n and the cubes p and q illustrate the comparison.
Weighing volume against air resistance in pounds
Taking q as three pounds and the air as resisting by one pound, the effective weight of three is reduced to two. The four lower dice at three pounds each make eight, and the upper make twelve, for twenty in all, which contains two ten times over, so the larger is reckoned ten times faster.