As is manifest by the [12 e. xviij]. And this is the invention or way to finde out the circular ray for an octoedrum, and an icosoedrum.
5 A mingled ordinate polyedrum of a triangular base, is either an Octoedrum, or an Icosoedrum.
This division also ariseth from the bases of the figures.
6 An octoedrum is a mingled ordinate polyedrum, which is comprehended of eight triangles. 27 d xj.
As here thou seest, in this Monogrammum and solidum, that is lines and solid octahedrum.
Therefore
7 The sides of an octoedrum are 12. the plaine angles 24, and the solid 6.
And