Plutarch, Theseus
Bernadotte Perrin, Ed.

In Eleusis, moreover, he out-wrestled Cercyon the Arcadian and killed him and going on a little farther, at Erineus, he killed Damastes, surnamed Procrustes, by compelling him to make his own body fit his bed, as he had been wont to do with those of strangers. And he did this in imitation of Heracles. For that hero punished those who offered him violence in the manner in which they had plotted to serve him, and therefore sacrificed Busiris, wrestled Antaeus to death, slew Cycnus in single combat, and killed Termerus by dashing in his skull. [2] It is from him, indeed, as they say, that the name ‘Termerian mischief’ comes, for Termerus, as it would seem, used to kill those who encountered him by dashing his head against theirs. Thus Theseus also went on his way chastising the wicked, who were visited with the same violence from him which they were visiting upon others, and suffered justice after the manner of their own injustice.