In 1907, American physician Duncan MacDougall from Haverhill, Massachusetts, USA, attempted to prove the existence of the human soul. For his experiment, he needed dying patients and several dogs, which he deliberately killed for this purpose. Although MacDougall claimed that he had managed to prove the existence of the soul and even determine its weight, scientists later debunked the results of the gruesome experiment, reports IFLScience.

MacDougall believed that the human soul has a physical weight and that it could therefore be measured on scales. The doctor assumed that when the soul leaves the human body, the body’s weight decreases, meaning that the difference between a person’s weight before death and at the moment of death would be the weight of the soul, which, he suggested, likely ascended to heaven.

To carry out the experiment, MacDougall built a special bed that functioned as a large set of scales, according to Focus. He found six volunteers — terminally ill patients dying from tuberculosis. These individuals were chosen because they remained still before death, which meant the scales could record an accurate measurement of their body weight before and after dying.

When a dying patient was placed on the bed, the scale was set to zero. The doctor then observed changes in body weight right up to the moment of death.

During the death of one patient, the experiment showed a weight loss of 21.3 grams. Other patients lost up to about 20 grams. MacDougall concluded that he had proven the existence of the soul and that it weighed approximately 21 grams.

He then decided to conduct a control experiment. He took 15 sick dogs, some of which he deliberately killed since they were dying slowly, and placed them on the scales. MacDougall claimed that animals had no soul to lose, and therefore should not become lighter after death. Indeed, according to his measurements, the dogs did not lose weight after death.

MacDougall published his findings in local newspapers and even in a scientific journal. However, scientists quickly dismantled the results of his bizarre experiment.

The results were flawed from the outset due to questionable methodology. MacDougall himself admitted that it was difficult to pinpoint the exact moment of death. Any changes in weight recorded in such a small sample of patients could be explained by increased sweating and the evaporation of moisture that occurs as body temperature rises shortly after death, since blood circulation ceases to cool the body. Dogs also sweat, but mostly through their paws, which means their weight loss after death would be minimal.