Joseph Campbell 
Papers from the Eranos Yearbooks, Eranos 4 [PDF ebook] 
Spiritual Disciplines

Essays by Rudolf Bernoulli, Martin Buber, C. M. von Cammerloher, T. W. Danzel, Friedrich Heiler, C. G. Jung, C. Kerényi, John Layard, Fritz Meier, Max Pulver, Erwin Rousselle, and Heinrich Zimmer. With an introduction by Mircea Eliade.
Originally published in 1960.
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