Some traditions assert that all Buddhas are emanations of Vairocana; in this view, Vairocana is understood as the first of the Buddha incarnations.
As it turns out, the first textual mention of Vairocana appears in the Brahma Net Sutra. The sutra teaching is given by Vairocana and, in the poem at the beginning (quoted in the last post), Vairocana describes herself this way:
All Buddhas have Vairocana as their original body. This body -- the one reading this post -- is the body of Vairocana. You have it, I have it, all innumerable beings have it.
Vairocana wholly manifests Buddhanature, which all beings have at all times.
In this way, the Brahma Net Sutra can be viewed as arising from and manifesting Buddhanature, enlightenment nature. And the 64 precepts described in the sutra simply describe the enlightened mind, the mind of a Buddha.