Symbols - What does heaven look like
When this term is used symbolically it is an alchemical term. The basic meaning is to change base metals into gold, but this is not a literal process. Thus transmutation isn’t some magical chemical process whereby one can change one metal to another [although many less spiritually inclined spent their whole lives thinking that this is what it meant and that the alchemists had found some secret process].
The transmutation is spiritual. One is changing oneself via the stages of the spiritual path from ‘base metal’ – a complete beginner – by gradual process of refinement and purification – to gold.
The alchemists also added another layer of meaning applicable when one used the sexual techniques as the means of obtaining experience – transmutation meant the ability to transmute physical ecstasy to spiritual ecstasy.