The Theogony of Hesiod

"From the Heliconian Muses let us begin to sing, who hold the great and holy mount of Helicon, and dance on soft feet about the deep-blue spring and the altar of the almighty son of Cronos, and, when they have washed their tender bodies in Permessus or in the Horse's Spring or Olmeius, make their fair, lovely dances upon highest Helicon and move with vigorous feet..."