Here is the original paper: https://www.newdualism.org/papers/D.MacDougall/soul-substance.htm
In short, taking into account every eventually and using very precise scales (for 1907) a man named MacDougall measured the body's weight for 6 people that died of conditions (like TB) where they would be non-moving and stable. The results indicate the human body weight about as much as a slice of bread less when the soul departs.
No good naturalistic/materialistic explanations for his results has not been found. MacDougall wanted to perform many more experiments, but opposition to the project made this impossible. The experiment has never been replicated on humans. Replications on animals show they gain weight at the moment of death. Strange.
Here is a decent summary of the issue, with the theory that perhaps the soul has some sort of psycho-kinetic effect on the weight of the body.
Ive watched the movie 21 grams before.
https://www.imdb.com/title/tt0315733/
Considering the time, I cant imagine weight was very accurate. Heres a interesting article about the problem. Took some remembering for this one.
https://www.npr.org/2009/08/20/112003322/this-kilogram-has-a-weight-loss-problem
I also think raw energy has no weight, although this seems to be a tricky question. I consider light a pure form of energy and if its photons had mass it wouldnt work.
However, perhaps when you die and your body starts flooding itself with dmt and other things. Maybe this chemical reaction converts a ton of fat or muscle or something else when it happens. Who really knows!
But it is something interesting to ponder. I certainly believe that when you die that isnt truly the end. You may not be able to take memories or maybe even feelings. But something continues somewhere, if not in the soul, then in the atoms and molecules that make up the body.
Afterall, we are just made of recycled stardust, thats all.