As we observe the writings in the Lotus Sūtra, we find 20 important doctrines, the first and second of which are the two doctrines of 3,000 dust-particle kalpa and 500 (million) dust-particle kalpa. The 3,000 dust-particle kalpa is preached in the “Parable of a Magic City” chapter of the Lotus Sūtra, fascicle 3: “Suppose a major world system (consisting of 1,000 X 1,000 X 1,000 worlds) was crushed into dust. A particle of dust was then dropped over 1,000 worlds traveling eastward until the dust was exhausted. After this, all the worlds that were passed over with or without dropping a particle of dust were crushed into dust. Suppose each of the dust particles thus produced stands for one kalpa. The total number of the kalpa is called the 3,000 dust-particle kalpa (aeons).”

Kyōdai-shō, A Letter to the Ikegami Brothers, Writings of Nichiren Shōnin, Volume 6, Followers I, Page 72