The Nuttall Encyclopedia
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.
Wood, James, ed. Entry for 'Eleusinian Mysteries'. The Nuttall Encyclopedia. http://www.studylight.org/encyclopedias/nut/e/eleusinian-mysteries.html. Frederick Warne & Co Ltd. London. 1900.