I'm pretty sure I stumbled over this story before, but this is a longer article about the scientist that tried to weight the human soul:
That the human body should be home to a physical soul which survived death was at one time rarely questioned. Then came the advent of scientific disciplines such as anatomy, chemistry and physics, whose probing and measuring raised awkward questions about where in the body a soul could live and what physical form it could take. With no medical proof being forthcoming, in 1854 the German anatomist Rudolph Wagner suggested that there must be a “special soul substance” in the body, evidence of which should be sought out by experimentation. Wagner was much ridiculed for his beliefs, and some years later his rival Ernst Haeckel mocked that at the moment of death it might be possible to liquefy the soul by freezing it and then “exhibit it in a bottle as immortal fluid”.
The nature of a human soul was a much-discussed topic within Victorian psychical research communities, many of whose members were also eminent scientists. Different philosophical conclusions were reached, but none was based on empirical evidence, it being deemed too difficult to measure any of the soul’s presumed physical properties. However, not everyone was prepared to accept this, and in the winter of 1896 Dr Duncan MacDougall, a Massachusetts-based surgeon, came up with a novel idea.