The twenty third Booke of Geometry, of a Prisma.
1 A Pyramidate is a plaine solid comprehended of pyramides.
2. A pyramidate is a Prisma, or a mingled polyedrum.
3. A prisma is a pyramidate whose opposite plaines are equall, alike, and parallell, the rest parallelogramme. 13 d xj.
As here thou seest. The base of a pyramis was but one: Of a Prisma, they are two, and they opposite one against another, First equall; Then like: Next parallell. The other are parallelogramme.
Therefore
4. The flattes of a prisma are two more than are the angles in the base.
And indeed as the augmentation of a Pyramis from a quaternary is infinite: so is it of a Prisma from a quinary: As if it be from a triangular, quadrangular, or quinquangular base; you shal have a Pentraedrum, Hexaedrum, Heptaedrum, and so in infinite.