Shortly after graduating from UCLA in 1917, Long moved to the island of Hawaii to teach in elementary schools. When he arrived, he claimed that some Native Hawaiians were practicing what he called magic. Long wrote that at first he was skeptical of this magic, but later became convinced that it worked. He devoted the rest of his life to creating theories about how the Native Hawaiians did what he claimed they did, and teaching those theories through the sale of books and newsletters.

Long decided to call his compilation of teachings Huna, because one meaning of the word is "hidden secret." He wrote that he derived it from the word kahuna, who were priests and master craftsmen who ranked near the top of the social scale.

There are no accepted Hawaiian sources - Malo, Kamakau, 'I'i, Kepelino - that refer to the word Huna as a tradition of esoteric learning.

Long founded an organization called the Huna Fellowship in 1945 and, starting in 1936, published a series of books on Huna that are still in print.

• The Secret Science Behind Miracles, 1948 (ISBN 0875160476)
• Mana or Vital Force, 1949
• Secret Science at Work, 1953 (ISBN 0875160468)
• Growing into Light, 1955 (ISBN 0875160433)
• Self-Suggestion and The New Huna Theory of Mesmerism and Hypnosis, 1958
• Huna Code in Religions, 1965 (ISBN 0875164951)
• Short Talks on Huna, 1978 (ISBN 0910764026)
• Recovering the Ancient Magic, 1978 (ISBN 0910764018) (originally published 1936)
• What Jesus Taught in Secret, 1983 (ISBN 0875165109)
• Tarot Card Symbology, 1983 (ISBN 0910764077)
• Psychometric Analysis

Hawaiian traditions

• Jensen & Jensen, Daughters of Haumea (Pueo Press, 2005)
• June Gutmanis, Kahuna La'au Lapa'au: Hawaiian Herbal Medicine (Island Heritage, 1976)
• E. S. Craighill Handy, Polynesian Religion (Kraus Reprint, 1971)
• Pali Jae Lee and Koko Willis, Tales From the Night Rainbow
• Makana Risser Chai, Na Mo'olelo Lomilomi: Traditions of Hawaiian Massage & Healing (Bishop Museum, 2005)