The Szilassi polyhedron and the tetrahedron are the only two known polyhedra in which each face shares an edge with each other face. Furthermore, the Császár polyhedron (itself is the dual of Szilassi polyhedron) and the tetrahedron are the only two known polyhedra in which every diagonal lies on the sides.
the szilassi polyhedron and the tetrahedron are the only two known polyhedra in which each face shares an edge with each other face furthermore the császár polyhedron (itself is the dual of szilassi polyhedron) and the tetrahedron are the only two known polyhedra in which every diagonal lies on the sides