a c b d e f

If two surfaces equal in quantity are superposed one upon the other, whatever of them touches will be equal one to the other. Therefore whatever of them does not touch will remain equal between them. And if a greater quantity of such surface, divided into equal or unequal parts, is superposed on different sides around an entire surface which is similar in quantity to all the pieces of the surface laid upon it, whatever of them touches will be equal, and consequently whatever of them does not touch remains equal. The various figures of the surfaces that do not touch, which are of curved lines, will be superposed on those of straight lines. And whatever exceeds beyond their contact remains equal, and those too can be re-set one upon the other infinitely, until you have your intent. When the superposition divides both the one and the other surface, it is not good, unless it already separates the rectilinear surfaces from the curvilinear surfaces.

the contact remains squared

1a, a, c d, b

3a, b, a, c

2a, o, n, m

Here I have 2 equal surfaces superposed one upon the other, that is the surface a c b and the surface c d. And the part c is common to the one and to the other, and the excess a b of the one is equal to the excess d of the other. Whence I will make of these pieces a b and d the second superposition, and the parts n o will be left equal, whence I will make of them the third superposition, and c will be a square from a.