The doctrine of three thousand realms in a single moment of life is found in only one place, hidden in the depths of the "Life Span" chapter of the essential teaching of the Lotus Sutra. Nagarjuna and Vasubandhu were aware of it but did not bring it forth into the light. T'ien-t'ai Chih-che alone embraced it and kept it ever in mind.

The Opening of the Eyes - WND-1, 224