To begin with, our Lord Preacher Śākyamuni Buddha is called Daigaku Seson (Greatly Enlightened World-Honored One). The Chinese character son of “Seson” means takashi (high), and it also means kō (filial piety). As Śākyamuni Buddha is the most filial of all dutiful children, He is called the World-Honored One. Śākyamuni Buddha has a golden body, and is equipped with 32 marks of physical excellence. One of His 32 marks is that no one can see the top of His head. The Buddha is 16 feet tall, but when non-Buddhists with bamboo sticks tried to measure His height with a 16-foot long bamboo stick, it was in vain. Even King of Brahma Heaven cannot see the top of His head. This is such an inexplicable physical mark of the Buddha. Why is the Buddha equipped with such an excellent mark as this? It is because He is a great being who is foremost in filial piety.

Hōren-shō, Letter to Hōren, Writings of Nichiren Shōnin, Volume 6, Followers I, Page 50-51