大毘盧遮那成佛經疏 17.15

17.15

As for the seventh mudrā, as with the previous saṃpuṭa, with both hands pinch earth and space together inside the palms and open the fire fingers, with the tips of the water and wind fingers joined together. The two earths are above the fire. The maṇḍala has the form of space (make it square), variegated and mingled with multiple colors; this is the color of space. Just as space contains all forms and images, so the Tathāgata's great emptiness gnosis contains all phenomena. Flank it with a dot on each of its two sides. The mantra is: