When Grand Master Dengyō of Japan dug the ground to build the Main Temple on Mt. Hiei, a key with eight tongues emerged. Later, he took the key with him when he sailed to T’ang China. There he met Venerable Tao-sui, the seventh patriarch of the T’ien-t’ai School and a disciple of Grand Master Miao-lê and was initiated into the T’ien-t’ai doctrine. Grand Master Dengyō was so genuine and intelligent by nature that Tao-sui was delighted to show him the fifteen storehouses of Buddhist scriptures built by Grand Master T’ien-t’ai. Fourteen of them were opened but not the last one. Grand Master Dengyō then requested, “Please open this storehouse.” Venerable Tao-sui replied, “There is no key to this storehouse. I believe that Grand Master T’ien-t’ai will appear some day again in this world to open it himself.” Grand Master Dengyō then took out the key that he had brought from Japan and opened it. When it was opened, rays of light generated in the storehouse brightened the room. Looking for the source of the light, they found it coming from the very sentence on the “three thousand existences contained in one thought” in the fifth fascicle of the Great Concentration and Insight. It was gracious and wonderful. Venerable Tao-sui, who transmitted the T’ien-t’ai doctrine to Grand Master Dengyo, bowed before his disciple, saying, “You are the avatar of Grand Master T’ien-t’ai.” In this way, all the books and scrolls of Grand Master T’ien-t’ai that had been kept in those storehouses were brought to Japan. At present in the Main Hall of the Enryaku-ji Temple on Mt. Hiei are the 25th chapter of the Lotus Sūtra, “Word-Voice-Perceiver Bodhisattva,” copied by Grand Master T’ien-t’ai and the Great Concentration and Insight recorded by Grand Master Chang-an.

Ichidai Shōgyō Tai-I, Outline of All the Holy Teachings of the Buddha, Writings of Nichiren Shōnin, Doctrine 3, Page 90-91