Book by Jessie L. Weston applying the methods of
cultural anthropology, developed originally by
James Frazer in The Golden Bough, to the
grail romances, and demonstrating their origin in
ancient pagen fertility rituals. Also used by
T.S. Eliot as basis for his epic poem The Waste Land.

Currently in the public domain, and can be found at
http://www.celtic-twilight.com/weston