Arcana of Nature (Barnes & Noble Digital Library)

This volume, which the author claimed was written by his “invisible guides,” explores the formation of the solar system, the development of life on Earth, the origin and history of the human race, the structure of the human brain, and the source of thought itself. After his guides set Tuttle back a few times, once even telling him to burn the manuscript—the work was eventually published in 1860. This edition also includes sections of an earlier work "The Philosophy of Spirit," which Tuttle wrote in his teens and later published as a second volume of the Arcana.