The twentieth-century frontier experiments conducted by Duncan MacDougall M.D. of Havervill, Massachusetts are worthy of mention. As a skeptic, it should be noted that MacDougall approached his research from a methodological naturalist’s point of view, writing with detectable resentment towards the blind faith demanded from theologians and so-called metaphysicians regarding the existence of the spirit / soul. Thus his experiments suffer from confirmation bias in that McDougall set out with a specific goal, to disprove existence of a soul that transcends death.
His hypothesis was simple enough:
…the soul substance so necessary to the concept of continuing personal identity after death of the material body must still be a form of gravitative matter…”
Hence it must have weight.