首楞嚴義疏注經 7.22

7.22

The milk of oxen from the Snowy Mountains is pure ghee, and all their waste is exceedingly fragrant and clean, so merely mixing it with sandalwood alone suffices to plaster the ground. If one lacks this, one digs deep for earth and additionally mixes in the ten kinds of miscellaneous fragrances to plaster the ground of the site. The octagonal altar matches its dimensions in circular area; it is made by clearing the ground, yet without terraces, which is what is nowadays called an open terrace (shan). Although the altar is octagonal, adding above and below makes ten, so as to correspond to the round number [of ten]. Below, the text mentions mirrors hung opposite each other with their light intersecting above and below, each mirror displaying the buddhas of the ten directions. This signifies that one body is precisely ten bodies, and ten bodies are precisely one body—infinitely overlapping, mutually manifesting, and mutually containing. This symbolizes the marks of the inconceivable realm of the tathāgatagarbha mind. Where the text below says that the buddhas of the ten directions all manifest simultaneously where the mirrors' rays intersect, it is precisely this mark.