Extending a straight line for 35 degrees from the star in the middle of the Cassiopeia's W through the star on its immediate lower right will place you in the middle of a large square forming the body of Pegasus, the winged horse.

The Square of Pegasus is comprised of Markab, Scheat, and Algenib in the constellation Pegasus and Alpheratz, which became part of the constellation Andromeda when the constellation boundaries were formalized in 1928 by the International Astronomical Union.