Cavern, difficult return, and permitted bough

Meaning

The fatal cavern is easy to enter but difficult to leave. The distinction makes access to hidden knowledge insufficient without successful return, and belongs beside the passage’s insistence that the treasure is offered broadly yet not equally attained.

The shining bough supplies a second condition: it follows willingly only after the fates permit it, and cannot be forced free by iron or violence. Heavenly favour and a pure hand qualify acquisition. The author invokes Virgil’s imagery for philosophical access rather than documenting an actual underground journey. Cavern and bough therefore explain danger, authorization and completion, not a map or a literal plant to procure.