How does a soul leave a body?

A medium recently said to me that he once saw his exact counterpart of himself, standing before him in the circle and that another person present saw the same. Will you explain this?

When the spirit leaves the body, life for the time being is a non-entity unless that be done in sleep. The spirit visits our world and carries back little except in certain dreams or visions, of which it becomes conscious to some extent in the normal state.

But in such a case, as the one you refer to, the spirit, after getting his likeness thrown on the eyeball would return at once, and the medium, of course, would then see his second self standing before him, though such was not exactly the case, for the object had passed away before he saw it pictured on the eyeball. In the same way, the light of certain planets will not reach you for a long time and when the light does appear to you, the bodies whence it comes do not occupy the same spot―they have passed away though to your vision they are apparently shining on you.

―Hafed, Prince of Persia