Precious Key to the Secret Treasury, The ［秘蔵宝鑰］ ( Hizō-hōyaku): A three-volume work by Kōbō (774–835), the founder of the Japanese True Word (Shingon) school. In the Tenchō era (824–834), when Emperor Junna ordered the Flower Garland (Kegon), Dharma Characteristics (Hossō), Three Treatises (Sanron), Precepts (Ritsu), Tendai, and True Word schools to submit a written statement of their fundamental teachings, Kōbō presented The Treatise on the Ten Stages of the Mind in ten volumes, setting forth the essential doctrines of the school. Because The Treatise on the Ten Stages of the Mind was so comprehensive, the emperor ordered Kōbō to make a summary of this work. The condensed version he produced in response is The Precious Key to the Secret Treasury. In it, Kōbō recapitulates the ten stages of the mind and asserts the superiority of the esoteric over the exoteric teachings. See also ten stages of the mind.