"one only has made the passage, and that was the celebrated Argo"

The Argo was the ship of Jason and the Argonauts. The event referred to here is an episode in the story of Jason and the Argonauts where they must sail through two dangerous, clashing rocks. Watch this video to see a clip from the 1963 film Jason and the Argonauts (bear in mind that this version differs in some ways from ancient Greek mythology).