Well, if you're going to bring up souls. Ask any group of adolescents, America's deep and informed body of film scholars, and they will tell you that the soul weighs 21 grams. They know this because there was a movie, although it wasn't really about soul weight even though the title alluded to it, called 21 Grams.
I don't know about your German scientists, Gil, but most allusions to a measurable soul weight refer to an American doctor, Dr. Duncan MacDougall, who, in 1907, conducted experiments on six terminally ill patients, weighing them immediately before and after death on a specially constructed bed "sensitive to a weight of less than one-tenth of an ounce." (The New York Times reported on his experiments in 1907.)
MacDougall believed his six experiments yielded four measurable results, which I have converted from ounces to grams:
0.75 oz. = 21.3 g
0.5 oz. = 14.2 g (a few moments later the total loss was 1.5 oz.)
0.5 oz. = 14.2 g (a few moments later the total loss was 1.0 oz.)
0.375 oz. = 10.6 g (a moment later the weight seemed to come back and loss was measured at 0 oz.)
You'll notice that it is only the first of the six experiments that popular culture has taken to heart. And while modern scientists discredit all of the experiments due to a suspect methodology and even MacDougall himself admitted that his sample size was wanting, writing in American Medicine, "I am aware that a large number of experiments would require to be made before the matter can be proved beyond any possibility of error" (Snopes.com), so that no rational basis for soul weight came from these experiments, this is clearly one of those concepts in which faith (not religious faith, just mere faith) trumps empiricism. After all, over a hundred years have gone by and we can still talk without laughter, in our classrooms!, about the weight of a soul.
MacDougall wrapped up his soul-searching career around 1911, trying to find a way to take pictures of the soul.
I would say all this is much ado about nothing (and thereby provide a segue back to our patient text), except I happened to read a couple years ago a little known science fiction novel by Andre Maurois ― The Weigher of Souls (1931). Like many great ghost and horror stories, the tale is told by an impartial observer who interviews the eponymous protagonist, Dr. Howard Bruce James. James describes some research he has come across:
"I once read an account, in a medical paper during the War, of an experiment made by a certain Dr. Crooks. He described how he had weighed the corpses of animals, and had observed that, after a period approximately regular in a given species, there was an abrupt drop in weight. … In man, he reckoned this fall as averaging seventeen-hundredths of a milligram. From which he concluded that the soul does exist, and that it weighs seventeen-hundredths of a milligram." (71)
For those of you without calculators at home, that's 0.17 mg or 0.00017 grams. Not bad accuracy for a WWI scientific measuring device.
Crooks is fiction, but his experiments, on animals, have a significant echo of MacDougall, who tried to get more consistent measurements with dogs. Finding people willing to die on his table must have been difficult. Maurois's Dr. James is less concerned with the weight of the soul, though, than its existence and specifically what happens to it after the physical body dies. The plot of the book focuses on his successful attempt to capture a soul, the soul of a man named William Slutter, and imprison it in a glass globe. Chapter 8 concludes thus:
"For after all, James, suppose that the law of human nature really is that a vital fluid escapes from our body after death, to merge with some universal resevoir of life, why and how should we stand in its way? Your globes are not eternal, and a day will come when, despite you, William Slutter will cease to be William Slutter. And what will you then have done but vainly prolonged an existence, under conditions which perhaps are dreadful? You have made an amazing discovery, and one which will give you one kind of fame when you choose to make it public … But you must confine the risk in these experiments to the bounds of strict necessity. 'There are more things in heaven and earth, Horatio …'"
"That reminds me," he said, "that I must take you to see Hamlet one evening … Good night!" (115-116)
All things, it seems, come back to Shakespeare.