When we had crossed the threshold of the door
Which the perverted love of souls disuses,
Because it makes the crooked way seem straight,
Re-echoing I heard it closed again;
And if I had turned back mine eyes upon it,
What for my failing had been fit excuse?
We mounted upward through a rifted rock,
Which undulated to this side and that,
Even as a wave receding and advancing.
“Here it behoves us use a little art,”
Began my Leader, “to adapt ourselves
Now here, now there, to the receding side.”