In S, "Sammai-O-Zammai," (the king of samadhis samadhi) Dogen writes: "Hence there is a mind sitting, and it is not the same as a body sitting. There is a body sitting and it is not the same as a mind sitting. There is sitting with body and mind cast off, and it is not the same as sitting with the body and mind cast off."
For a mind sitting there is nothing apart from mind, and thus it is different from a body sitting. The same holds true for a body sitting. As one side is illumined, the other is darkened. Yet sitting with body and mind cast off is not transcendence of body and mind, but the being time of sitting as entire being/ entire time.