21 grams experiment
In 1901, Duncan MacDougall wanted to find out if a soul had weight. He found six patients in nursing homes who were going to die soon. Four had tuberculosis, one had diabetes, and one had other causes. MacDougall chose people who were very tired because of their illness. He needed them to be still when they died so he could measure them accurately. When the patients were close to death, their whole bed was put on a big scale. The scale was sensitive within two tenths of an ounce (5.6 grams). MacDougall thought that humans have souls but animals do not. So he later measured the weight changes of fifteen dogs after they died. MacDougall wanted to use sick or dying dogs for his experiment. But he could not find any. So it is thought that he poisoned healthy dogs.