In this poem Mercurius is describing his own transformation, which at the same time signifies the mystic transformation of the artifex; for not only Mercurius but also what happens to him is a projection of the collective unconscious. This, as can easily be seen from what has gone before, is the projection of the individuation process, which, being a natural psychic occurrence, goes on even without the participation of consciousness. But if consciousness participates with some measure of understanding, then the process is accompanied by all the emotions of a religious experience or revelation.
— Carl Gustav Jung
Jung is describing something that will not wait for your permission. The individuation process runs — in dream, symptom, compulsion, the recurring figure you cannot explain — whether or not a single waking thought is ever directed toward it. Mercurius transforming is the unconscious transforming itself, and the alchemist watching is incidental to the chemistry. This is worth sitting with before the next sentence seduces you into something easier.
The seduction is real. "All the emotions of a religious experience or revelation" — consciousness participates and suddenly the process becomes luminous, felt, charged with meaning. That is not wrong. But hear what it quietly offers: the promise that awareness converts raw transformation into something you can inhabit, that understanding earns you a seat at the table of your own depth. The pneumatic current runs directly through this reading. Spirit is the reward for showing up. The revelation is the payoff. What goes unremarked is that the process was already happening — in the body, in the pattern, in the compulsion that returned before you named it — and that the luminosity, real as it is, does not alter the mechanics. The unconscious is not impressed by your participation. It simply becomes, at last, audible to you.
Carl Gustav Jung·Alchemical Studies·1967