佛祖統紀 30.39

30.39

When it increases to twenty thousand years, an iron-wheel-turning king will appear and rule the southern continent alone (The Abhidharmakośa-bhāṣya states: gold, silver, copper, and iron wheels correspond to one, two, three, and four continents; an iron-wheel king rules one continent, a gold-wheel king rules four continents). When it increases to forty thousand years, a copper-wheel-turning king will appear and rule the two continents of the east and south. When it increases to sixty thousand years, a silver-wheel-turning king will appear and rule the three continents of the east, west, and south.