妙法蓮華經玄贊 4.62

4.62

儴佉劫增時出，命長故逢彌勒，非彌勒佛不減時出。又佛不出家應為金輪之位，非定作也。燈明八子義理亦同，彼是報身故無此失。此說金輪必劫增出，銀銅鐵輪王出時不定，是以無憂王世，佛滅百年，鐵輪王也。

Śaṅkha appears when the kalpa increases, and because his life is long he meets Maitreya; it is not that Maitreya Buddha appears when the kalpa is not decreasing. Furthermore, if a buddha does not leave the household life, he ought to assume the position of a golden-wheel king, but he does not definitely do so. The meaning is the same for the eight sons of Candrasūryapradīpa; because those were reward bodies, there is no such fault. This applies to the golden-wheel kings who must appear when the kalpa increases; the times when silver-, copper-, and iron-wheel kings appear are not fixed. Therefore, King Aśoka in the era one hundred years after the Buddha's nirvāṇa was an iron-wheel king.