Huber sent a paper Richard P. Jerrard and John E. Wetzel: "Universal Stoppers Are Rupert" College Mathematics Journal 39,2 (March 2008) 90-94 containing the pathblazing adjective "Rupert”, meaning Rupertable, plus pointing out that the regular tetrahedron, icosahedron, dodecahedron (i.e. all 3D regular polyhedra, since cube & octahedron are too) allegedly are Rupertable. Tetrahedron: Christoph J. Scriba, Das Problem des Prinzen Ruprecht von der Pfalz, Praxis der Math. 10 (1968) 241-246. Icos & Dodec: Richard P. Jerrard and John E. Wetzel, Platonic passages, 07 T-51-2, Abstracts Amer. Math. Soc. 28 (2007) 351. Prince Rupert generally: D. J. E. Schreck: Prince Rupert’s problem and its extension by Pieter Nieuwland, Scripta Math. 16 (1950) 73-80, 261-267. Also of course the regular N-gon in 2D is Rupertable with expansion factor sec(pi/N) if N=even 2*cos(pi/(2*N)) / (cos(pi/N)+1) if N=odd. So, only the sporadic 4D regular polytopes (and perhaps high-dimensional regular simplices) remain of unclear Rupertability... unless somebody already did them too... Warning: I have not seen these papers. -- Warren D. Smith http://RangeVoting.org <-- add your endorsement (by clicking "endorse" as 1st step)