[I]n asking their parents’ permission — a requirement of the monastic rule — to renounce household life and become Buddhist monks, the two princes state that it is “difficult to meet a buddha, just as it is to see udumbara flowers or for a one-eyed turtle to find the hole in a floating piece of wood.” The uḍumbara tree was said to bloom once every three thousand years and thus stands as a symbol for an extremely rare opportunity. The same analogy occurs in the “Skillful Means” chapter to illustrate the rarity of hearing the Lotus Sūtra.

The analogy of the turtle and the floating piece of wood appears in a number of sūtras and commentaries, where it is used to illustrate the rarity of being born human and encountering the Buddha’s teaching. In a letter to a follower, the wife of the same Matsuno Rokurōzaemon mentioned above, Nichiren develops the analogy in great detail and applies it specifically to the Lotus Sūtra. To summarize his expanded version: A large turtle with only one eye and lacking limbs or flippers dwells on the ocean floor. His belly is burning hot, but the shell on his back is freezing cold. Only the rare red sandalwood has the power to cool the turtle’s belly. The turtle yearns to cool his belly on a piece of floating red sandalwood and at the same time to warm his back in the sun. However, he can rise to the ocean’s surface only once in a thousand years, and even then, he can rarely find a piece of floating red sandalwood. When he does so, it may not contain a hollow, or at least not one of the proper size to hold him. Even when he finds a floating sandalwood log with an appropriate hollow place, without limbs, he cannot easily approach it, and having only one eye, he mistakes east for west; thus, he cannot accurately judge the direction of the log’s drift and winds up moving in the wrong direction. Nichiren interprets: “The ocean represents the sea of the sufferings of birth and death, and the turtle is ourselves, living beings. His limbless state indicates our lack of good roots. The heat of his belly represents the eight hot hells of anger, and the cold of the shell on his back, the eight cold hells of greed. His remaining for a thousand years on the ocean floor means that we fall into the three evil paths and are unable to emerge. His surfacing only once every thousand years illustrates how difficult it is to emerge from the three evil paths and be born as a human even once in immeasurable eons, at a time when Śākyamuni Buddha has appeared in the world.”

The turtle mistaking east for west, Nichiren continues, means that ordinary people in their ignorance confuse inferior and superior among the Buddha’s teachings, clinging to provisional teachings that have lost their efficacy and rejecting the one teaching that can lead to enlightenment. And the rarity of the turtle finding a floating sandalwood log with a hollow in it just big enough to hold him means that “even if one should meet the Lotus Sūtra, it is rarer and more difficult still to encounter the daimoku, which is its heart, and chant Namu Myōhō-renge-kyō.” In this way, Nichiren stressed the inconceivable good fortune of his followers, who had not only been born as humans and met the Lotus Sūtra but, although living in a degenerate age in a remote country far from the Buddha’s birthplace, were able to chant the wonderful dharma of the daimoku.