I doubt any computer you can lift will kill you if you put it on your lap. It might be uncomfortable, but it won't kill you. (I'm not about to put some of VAXen I've seen on my lap even though I can technically lift them, but...)

People do all kinds of terrible things to their body. That you do something and seem to be getting away with it doesn't mean you should. Talk to a real doctor trained in this (your regular doctors probably is not) for details.