John Muir (1997). “Nature Writings: The Story of My Boyhood and Youth, My First Summer in the Sierra, the Mountains of California, Stickeen, Selected Essays”, p.817, Library of America
"Hoyt's New Cyclopedia Of Practical Quotations" by Jehiel Keeler Hoyt, p. 461, The Literary Character, Illustrated by the History of Men of Genius (1795-1822), Chapter XXII, 1922.