Mason was the son of Rufus and Prudence Mason. He prepared for college at Thetford, Vermont, and later graduated at Dartmouth College in 1854. He then entered Union Theological Seminary before moving to medicine. In 1859, he graduated at the College of Physicians and Surgeons in New York City. He became one of the most noted surgeons of his day in New York City. During The American Civil War, he became an assistant surgeon for The United States Navy. From 1861 to 1864 he served on the USS Santiago de Cuba. In 1864 he took up medical practice in New York City, where he was attending physician, Northwestern Dispensary, until 1869. Between of leaving Union Theological Seminary and entering the medical profession, he became an instructor at a public school in Cleveland, Ohio. It was there that he met, taught, inspired, and befriended "A small Barefoot Boy," William Rockefeller. The relationship would endure through the years, and Mason became "A Rockefeller Patron" toward the advancing of the medical sciences. Mason was also deeply interested in metaphysical speculation and theory. His input would help in the early pioneer development of parapsychology and psychical research. These subjects were published in many books, magazines, and newspaper articles. He is accredited as "An Early Father-Pioneer of Parapsychology" and advance-supporter of the study of applied therapeutic uses of what is known today as Hypnotherapy. He was a contributing member of The Society for Psychical Research. His main publication was the book Telepathy and the Subliminal Mind, and his work focused on case studies and popularization. His chief contributions to the field are considered to be the latter, in the United States, particularly relating to the work of the Society for Psychical Research and the theories of Frederic William Henry Myers. Much of Mason's research and observations in psychical research would be applied in early ESP, Telepathy, Astral research, and in present-day remote Viewing. The 50th Annual Convention of the Parapsychological Association, September 2007, acclaimed him as an early pioneer in parapsychology and psychical research. He was married first in New York City to Marian Isabelle Goodwin in July 1871, and married second to Charlotte Louise Quick in 1886. After his death the latter used her inheritance to become a leading patron of the Harlem Renaissance.
