-- | Given in Sorokina and Zeilfelder, p. 79. Note that the third and
-- fourth indices of c-t3 have been switched. This is because we
-- store the triangles oriented such that their volume is
-- | Given in Sorokina and Zeilfelder, p. 79. Note that the third and
-- fourth indices of c-t3 have been switched. This is because we
-- store the triangles oriented such that their volume is