John James Audubon (1835). “Ornithological Biography: Or An Account of the Habits of the Birds of the United States of America; Accompanied by Descriptions of the Objects Represented in the Work Entitled The Birds of America, and Interspersed with Delineations of American Scenery and Manners. 5 Vol. Il. Q.”, p.165
John Muir (2015). “John Muir’s Incredible Travel Memoirs: A Thousand-Mile Walk to the Gulf, My First Summer in the Sierra, The Mountains of California, Travels in Alaska, Steep Trails… (Illustrated): Adventure Memoirs & Wilderness Studies from the Naturalist, Environmental Philosopher and Early Advocate of Preservation of Wilderness, the Author of The Yosemite and Picturesque California”, p.14, e-artnow