Wrestle Achelous

And having come to Calydon, Hercules wooed Deianira, daughter of Oeneus. He wrestled for her hand with Achelous, who assumed the likeness of a bull; but Hercules broke off one of his horns. So Hercules married Deianira, but Achelous recovered the horn by giving the horn of Amalthea in its stead. Now Amalthea was a daughter of Haemonius, and she had a bull's horn, which, according to Pherecydes, had the power of supplying meat or drink in abundance, whatever one might wish.


- Apollodorus, Library, Book 2, Chapter 7, Section 5