The fourth hell is called the Hell of Wailing, located beneath the Hell of Crushing. The size of this hell is the same as the Hell of Crushing. Hell guards shout in a dreadful voice, shooting arrows at sinners. They also strike sinners’ heads with iron bars, forcing them to run on the hot iron ground or burn them in a hot iron toaster, turning them over many times. Or they forcibly pour boiling copper fluid into the mouths of sinners so that the burned intestines drip down instantaneously.

Regarding the life span of the sinners in this Hell of Wailing, one day in the human world corresponds to 400 years in the Tuṣita Heaven, the fourth heaven in the realm of desire, where dwellers live as long as 4,000 years. Suppose 4,000 years in this Tuṣita Heaven are equal to one day in the Hell of Wailing, sinners in this hell have to suffer as long as 4,000 years.

Ken Hōbō-shō, A Clarificaton of Slandering the True Dharma, Writings of Nichiren Shōnin, Doctrine 3, Pages 108.