In 1907, Massachusetts physician Duncan MacDougall conceived a singular experiment. When he observed that a patient at his Haverhill hospital was nearing death, he installed him in a specially constructed bed in his office and measured his weight both before and after death. With six such weighings he determined that humans lose between 0.5 and 1.5 ounces at death.

“Is the soul substance?” he wrote. “It would seem to me to be so. … Here we have experimental demonstration that a substance capable of being weighed does leave the human body at death.”

Similar experiments with 15 dogs showed no change in mass, proving, he decided, that dogs have no souls. MacDougall’s findings were written up briefly in the New York Times and occasioned a flurry of correspondence in American Medicine, but after that they were largely forgotten. But who knows? Perhaps he was right.