According to Scientology dogma, the soul has no mass.
The 21 grams is the weight of the mind, the accumulated mental image pictures from the life just left.
How heavy a burden will you or I carry when we leave?
“the soul has no mass”
The soul has mass, especially if it is a fearful, angry one.
The purpose of religion is to help people decrease the mass and/or purify the soul. Consciousness has mass. I feel people’s thoughts as physical tangible objects. It’s easy to prove as I can stand several feet from a person and knock them over merely by touching the traumatic memories stored in their soul. The body exists in the soul, not the other way around.
Naturally, I think of the weighing of the heart, in particular, the ‘prayer of Ani’, from the Egyptian ‘Book of the Dead’:
“My heart, my mother; my heart, my mother! My heart whereby I came into being! Do not bear witness against me at the judgment.”