Another interesting little tid bit is described by Campbell ("Hero with a Thousand Faces") - page 89 - "The wall of paradise....the coincidence of opposites, it's gate being guarded by the highest spirit of reason...these are the clashing rocks of Symplegades...but Jason, in the Argo, sailed between, and since that time they have stood apart."
This interesting aspect of the First Threshold can also be seen as the door or gate in which the hero passes through and after he or she crosses there is no return. I liked this image so in Chapter Fourty-One, Down the River at Last, I replay this scenario in the Hole and the Chute. So in a fun way, this is the story of Jason and Argo. In the Chronicles, Charlie, Loki and the Morianders run the rapids on the Courageous River and pass through and down the Hole and the Chute (the crashing rocks of "Symplegades.")
I had a lot of fun trying to replicate that part of the hero's journey....stay tuned for more.