首楞嚴義疏注經 7.22

7.22

雪山牛乳純是醍醐，所有茹退最為香潔，但和一味旃檀即可塗地。苟無此者，即取深土，別加眾香十味和合以塗場地。八角之壇，方圓應量，除地為之，仍無級數，即今墠也。壇雖八角，上下為十，以應圓數。以下文有懸鏡相對，上下交光，一一鏡中現十方佛，以表一身即十身、十身即一身，重重無盡，互相顯現，互相容受。即表證藏心不思議境界之相也。下文十方諸佛一時俱現鏡交光處，是此相耳。

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.