Thanks for this interesting profile of Prentice Mulford, Mitch. You failed to mention Mary Baker Eddy (1821–1910), the founder of Christian Science—an extraordinarily popular metaphysical healing movement which the press coined the "Boston craze." New Thought sprung up in this "mind cure" atmosphere—it would not exist without Eddy. The phrase "Mind over matter" doesn't mean what you think it means. In Eddy's groundbreaking book, Science and Health—first published in 1875—Eddy wrote that "thoughts are things" (p. 261). She often expanded on this concept: “Divine Science, rising above physical theories, excludes matter, resolves things into thoughts, and replaces the objects of material sense with spiritual ideas” (p. 123, italics are hers). Her unique view was that everything is spiritually mental, not physically material. She insisted on the reality of spirituality and the unreality of matter—on the Allness of God and therefore the unreality (i.e., impotence) of evil. Her radical ideas many folks (such as the likes of Mulford) borrowed, bastardized, and often misunderstood. Her concepts may have become watered down over the years into what we have today: New Thought, New Age, and the mind-body-spirit connection. They’re all thanks to Eddy.
Today Christian Science still stands as the most idealistic and radical view, which heals through Mind (God) alone, rather than the human mind or human will.
Eddy was very well-known in her day, arguably as well-known as Oprah Winfrey in our time. Her seminal book remains a best-seller even now; and in 1992 it was designated by the Women's National Book Association as one of "75 Books by Women Whose Words Have Changed the World."