What's generally meant by the mind being separate from the body is that the idea that we control our bodies by thinking is actually an illusion. The way Buddhists know this is that in the body starts controlling itself without any input from the mind, something you can experience relatively easily from meditating. It only took me about 6 or 7 days to achieve the beginnings of this. (Scared the crap out of me, but it was insanely cool at the same time.)