1. The first of the figures on a plane surface is the circle, a
figure that is plane, and has a circumference, in the middle of which
is a point upon which everything converges (_cuncta convergunt_)
which geometers call the center, and the Latins call the point of the
circle.
2. A quadrilateral figure is one on a plane surface, and it is
contained by four straight lines....
3. A sphere is a figure of rounded form equal in all its parts.
A cube is a solid figure which is contained by length, breadth, and
thickness.
5. A cone (_conon_) is a solid figure which narrows from a broad base
like the right-angled triangle.
6. A pyramid is a solid figure which narrows to a point from a broad
base like fire. For fire in Greek is called πῦρ.
7. Just as all number is contained within ten so the outline of every
figure is contained within the circle.