Albert Michotte was famous for his work on the perception of causality, especially on the conditions under which one ball is visually interpreted as launching another. Less well known are his remarks on the experience of embodiment, which I just came across and can't resist sharing.
[W]here the body is motionless... there is an almost complete adaptation of the receptor organs, and the result is that the body simply disappears from the phenomenal world. This is indeed what seems to happen to a very high degree in the practice of certain oriental sects, where those who are expert are able, by remaining motionless, to achieve an extreme state of apparent "spiritualisation". Movement appears to be essential to the phenomenal existence of the body, and it is probable that we are aware of our bodily states only in so far as they are terminal phases of movements. In our ordinary waking life, of course, our bodies are motionless only to a relative extent; there is nearly always movement, if only as a result of respiration.Close your eyes, refrain as much as possible from touching anything. Do your pseudopodia grow and shrink as you move or refrain from moving them?
Whether it is temporarily motionless or whether it is moving, the body appears as a somewhat shapeless mass or volume. there is very little by way of internal organisation or connexion between the parts. There is no clear marking off of the head, trunk, and limbs by precise lines of demarcation.... Instead of any precise line of demarcation we find a number of regions with extensive connexions between them gradually merging into one another.
We can with some justification look on the body as a sort of kinaesthethic amoeba, a perpetually changing mass with loose connexions between the parts, and with the limbs constituting the pseudopodia.... The "volume" of which it consists is not limited by a clearly defined surface, and there is no "contour".... The limit of the body is more like the limit of the visual field -- an imprecise frontier which has no line of demarcation, and indeed which cannot without absurdity be imagined to have one (1946/1964, p. 203-204).