I have never seen it done- but i have tried to do it an di have always thought of it as one of those things that can be done (as Schaz says- it is just manipulation of energy fields) but that its our own negative mind blockage that stops us-

In saying that though- while i beleive it can be done i have tried and i reckon my mind is fairly open to it- but it still hasnt worked for me- maybe i just dont know exactly how to do it right!!