Kaleidoscope with One Horizontal and Two Vertical Mirrors
This Demonstration shows a kaleidoscope with one horizontal and two vertical mirrors. You can set the dihedral angle between the vertical mirrors to be , where .
 W. W. Rouse Ball and H. S. M. Coxeter, Mathematical Recreations and Essays, 13th ed., New York: Dover Publications, 1987 pp. 155–161.