It might yet be quantifiable; the process just may be beyond your world's current understanding. Who is to even say that a soul can be measured in weight and mass? Perhaps it merely adheres to rules that have yet to have been discovered.

[There are many ways in which a soul (or the essence of one's life, in general) and technology can be merged in a number of (sometimes questionable) ways. Ardyn knows this also from first-hand experience.]

A magic ring, and gifted by the gods, at that. Surely they're allowed to bend the rules now and again.