William Blake

Not a Gnostic in any historical line — he had almost certainly read none of these texts — but he independently produced a creator-figure of law and measure (Urizen, with his compasses) beneath a fuller divine imagination, and a poetry of the human as an imprisoned infinity.

The clearest case in the pack of convergence with no possible channel. If a London engraver can arrive at a demiurge from scratch, the position may be reachable from the human situation itself rather than from any tradition.