Eleusinian Mysteries, rites, initiation into which, as religiously conducive to the making of good men and good citizens, was compulsory on every free-born Athenian, celebrated annually at Eleusis in honour of Demeter and Persephone, and which lasted nine days.
Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)
Elephantine * Eleusis