Procrustes was a robber of Attica, who placed all who fell into his hands upon an iron bed. If they were longer than the bed, he cut off the redundant part; if shorter, he stretched them till they fitted it. Any attempt to reduce men to one standard, one way of thinking, or one way of acting, is called placing them on Procrustes' bed, and the person who makes the attempt is called Procrustes. (See Girdle.)
Tyrant more cruel than Procrustes old, Who to his iron-bed by torture fits Their nobler parts, the souls of suffering wits.
Source: Dictionary of Phrase and Fable, E. Cobham Brewer, 1894