Hesiod. Works and Days. (Lines 750-759).
Do not let a boy of twelve years sit on things which may not be moved (*H39), for that is bad, and makes a man unmanly; nor yet a child of twelve months, for that has the same effect. A man should not clean his body with water in which a woman has washed, for there is bitter mischief in that also for a time. When you come upon a burning sacrifice, do not make a mock of mysteries, for Heaven is angry at this also. Never make water in the mouths of rivers which flow to the sea, nor yet in springs; but be careful to avoid this. And do not ease yourself in them: it is not well to do this.