大毘盧遮那成佛經疏 17.8

17.8

As for the third mudrā, form it as before, namely with a saṃpuṭa añjali; the two water and fire fingers are separated, and the earth and wind fingers, having been opened earlier, form the shape of a newly blooming flower. This is the tathāgatagarbha mudrā, also called the lotus-garbha mudrā. The maṇḍala is made as a round moon disc as before, differing only in being surrounded by four lotuses; within it one likewise visualizes Mahāvairocana Tathāgata. Its mantra is: