The sections in b2, b3 will be like the section in b1 but smaller.
Finally in b4 the section plane simply passes through the corner named sin.
Hence, putting these sections together in their right relation, from the face setat, surrounded by the lines and points mentioned above, there run:
- 3 faces: satan, sanat, satet
- 3 lines: sanan, sanet, sat
and these faces and lines run to the point sin. Thus the tetrahedron is completely named.
The octahedron section of the tesseract, which can be traced from [fig. 72], p. 129 by extending the lines there drawn, is named:
Front triangle selin, selat, selel, setal, senil, setit, selin with area setat.
The sections between the front and rear triangle, of which one is shown in 1b, another in 2b, are thus named, points and lines, salan, salat, salet, satet, satel, satal, sanal, sanat, sanit, satit, satin, satan, salan.
The rear triangle found in 3b by producing lines is sil, sitet, sinel, sinat, sinin, sitan, sil.
The assemblage of sections constitute the solid body of the octahedron satat with triangular faces. The one from the line selat to the point sil, for instance, is named selin, selat, selel, salet, salat, salan, sil. The whole interior is salat.