hyperpyramid

The simplest case of a hyperpyramid is a figure called a pentahedroid.

The Fourth Dimension Simply Explained 1910

In general, the boundary of a hyperpyramid consists of the polyhedron base and of lateral pyramids resting on the faces of the base.

The Fourth Dimension Simply Explained 1910

The two pyramid bases have, then, a common polygon base and the hyperpyramid may be considered as determined by a polygon and tw points not both in a three-space with the polygon.

The Fourth Dimension Simply Explained 1910

A hyperpyramid whose base is a pyramid may be regarded in two ways as a hyperpyramid, the vertex in either case being the vertex of the pyramid base in the other case.

The Fourth Dimension Simply Explained 1910

These five points, taken four at a time, give us five tetrahedrons and the pentahedroid may be taken in five different ways as a hyperpyramid.

The Fourth Dimension Simply Explained 1910