21 grams is a project built around Duncan MacDougall’s experiment, which he made at the beginning of the 20th century. According to him a few minutes after death people lose approximately 21 grams of their weight, he called this the weight of the soul. The experiment was said to be controversial even in its time, the results were inconclusive however it gained big publicity and became a myth.
Recently I found a pack of negatives of my family from the beginning of the 20th century. The only living person from the pictures is my uncle who could not identify all of the people in the photographs. The portrait of an unidentified person (supposedly the daughter of a family friend) was enlarged onto 21 grams of pure photographic emulsion, which due to its qualities, dries and darkens over time, as well as loses most of its weight.