A force of 12 lifts 11 - and infinitely more, but never 12
Equal weights cannot overcome one another; the unit from 11 to 12 divides to infinity
In the principal column Leonardo argues that a force ('Piero') able to lift 12 cannot move a weight of exactly 12, because equal quantities do not overcome one another, but it will raise 11 and, since the unit between 11 and 12 is a continuous quantity divisible to infinity, it can raise 11 1/2, then 11 2/3, then 11 3/4, and so on without end. He draws out the paradox that a man is thereby in power to carry infinitely more weight than he can carry, while the smallest completing weight is the one he cannot lift. The marginal column restates the case beside a small balance diagram with the weights 3 and 4: a force matching 4 resists but cannot move it, yet it moves 3 and infinitely more than 3, but never a weight equal to 4.
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Why a power of 12 cannot move a weight of 12
A force able to lift 12, given exactly 12 of weight, does not move it, since equal things do not overcome one another. Among unequal powers the greater overcomes the lesser, so the force of 12 will instead move 11.
The unit from 11 to 12 is divisible to infinity
Because every continuous quantity is infinitely divisible, the single unit between 11 and 12 can be subdivided without end: the force moves 11, then 11 1/2, then 11 2/3, then 11 3/4, ever subdividing the remainder. Hence a man is in power to bear infinitely more than he can bear, while the least completing weight is the one he cannot carry.
Balance example: a force of 4 resists 4 but moves only 3
In the balance, 4 resists 4 but cannot move it. It will move 3 and infinitely more weight than 3, but never a weight equal to 4, because from 3 to 4 lies a unit that is a continuous quantity divisible to infinity.