Letter to Werner Zimmermann. June 20th 1936
From Spec. Ed. Mensch und Technik, Vol. 2, 1993, section 7.4.
Read "The Ox and the Chamois" again. There you will find precisely the opposite preconditions, namely the release of energy through cold. Here heat
 See "The Ox and the Chamois" in Nature as Teacher, p.41, Vol. II of the Ecotechnology series. — Ed.] [The Energy Evolution - Harnessing Free Energy from Nature, Letter to Werner Zimmermann]