"Because the true existence of the Tetsugi Masters passes through all the Buddhas of the Three Existences (of the past, present and future), and has passed through our Great Founder, through the successive generations of High Priests, shedding each in turn, you must be very, very careful to believe this with all your being, and my disciples must believe in me in exactly the same way." -- 9th Nichiren Shoshu High Priest, Nichiu Shonin [believed to have died a leper after fabricating the DaiGohonzon]
"Kuden transmission was a common practice of the Tendai Sect and derived from the false belief that the enlightenment of various teachers, "Shikan" or personal insight, trumped the wisdom of the scriptures. This is a dangerous teaching according to Nichiren because it destroys faith in the Scripture of the Fine Dharma of the Lotus Flower Sutra. Embracing such a false doctrine, one comes to the mistaken belief that personal insight may reveal things that contradict or superscede the teachings of the Buddha. It relies on the notion that there are "Kuden" (secret teachings) that can be passed by hand [or mouth] and in the case of the Nichiren Shoshu teachings that Buddhahood itself can be "passed" from one "Tetsugi Master" to another.
The origin of secret transmission doctrines within the Tendai Sect was largely a response to the gentrification of the Priesthood as more and more nobles entered the priesthood and some means had to be found to short circuit the years of training and demonstrated mastery otherwise required in order to qualify a priest for the Chief Priesthood of a Temple. It also was based on the incorrect notion that since enlightenment is found within all beings there is no need for cultivation of enlightenment or use of Buddhist logic. Masters could awaken and pass on hidden meanings. The extreme extension of the logic is the Zen Sect. Nichiren Shoshu's use of it is no less poisonous. Such a "transmission" is useful to quell not only dissent but legitimate questions.
Nichiren attacked this entire approach to his teachings so it is odd that Nichiu should have relied on such an approach to establish the legitimacy of his school. It is no wonder that Nichiren Shoshu had such a hard time of it among the other schools and that it wasn't until very recently that they established their own University but they still send their monks to the University established by the Minobu School [Rissho University] for advanced education." -- author unknown
*Tendai [Mikkyo] is a mixture of Tentai and Shingon practices