Medusans are known throughout the Federation as mathematical and navigational experts without equal. Their thoughts are the most sublime in the galaxy, however, their physical appearance so utterly hideous that the sight of a Medusan would render a human mad. Vulcans are capable of viewing Medusans, but only with the use of a specially filtered visor. For these reasons, Medusans usually use an opaque carrier pod when interacting with other species. (TOS: "Is There in Truth No Beauty?")