The five 4-Polyominoes, known as Straight, L-, T-, Square, and Skew.
References
Gardner, M. ``Polyominoes.'' Ch. 13 in The Scientific American Book of Mathematical Puzzles & Diversions.
New York: Simon and Schuster, pp. 124-140, 1959.
Hunter, J. A. H. and Madachy, J. S. Mathematical Diversions. New York: Dover, pp. 80-81, 1975.