Dr. Duncan MacDougall (1866 – 1920) measured the weight lost when terminally ill patients died. The average weight lost was 21 grams. He believed that the weight lost was due to the human soul leaving the body. He also measured dogs and found no weight lost upon death.

[link to en.wikipedia.org]

Here's a more detailed account:

[link to www.snopes.com]


Hasn't anyone tried to replicate this experiment? My guess is that answer is yes, and there was no weight loss, so people stuck with this "urban legend"