...of the circle into 16 pyramids, of which you know that every 3 pyramids make one whole, because you divided the 5 into thirds, which were 15 thirds, and then you added the 1/3 that stood above the line and you had 16/3. Now you know that 3 of these such pyramids compose one whole part. Hence 4 of these parts are the ones I have to subtract from the half-circle, and the question will remain solved. These 4 parts carry 12 of the said pyramids, at 3 per part. There remained 4 to go up to 16, which was the whole number. Therefore the 4 pyramids are 1/4 of the 16, and the 12 that were subtracted are the three-quarters of 16. Four is the three-quarters of what number? Do thus: 4 [and] 3/4. Say: '4 times 4 makes 16', and divide by the 3 that stands above the line and you will have 5 and 1/3. Then you will say: '3 times 5, 15', add the one that stands above the line, and you will have 16/3, and this is the number of pyramids into which the circle must be divided. And then draw off 4 whole ones, which contain 12 pyramids. And if you wish to know more briefly of what 4 is the 3/4, add to 4 one third of its quantity, which is one and 1/3, and you will have 5 and 1/3. Then make them all thirds and you will have 16/3. So here you have 3 methods.

a b c

g, d c f

If a curvilinear pyramid must be divided into 2 equal parts along its length, dividing the base in half, you must make the circle of the lesser curvature within the circle of the greater curvature c, and take the line b, and this will be a line of middle curvature. Then, placed at g c, between g d and g f, and thus you will cut that pyramid into 2 equal parts upon the base d f, with the point c.

When the curvatures of the curvilinear pyramid are equal, that is of its sides, the curvature of the middle line must be of the same curvature as the others.