|View looking NE into the Cascade Mtns. from Mount Rainier National Park.|
The incident is found on p. 31 of Snyder's book The Practice of the Wild, which is on my hypothetical desert-island book list.
And that whole brief era is described in detail in John Suiter's Poets on the Peaks.
It was probably the same summer that the two of them encountered a party of anglers on a forest trail and Ginsberg intoned, "WE are forest beatniks." A line that I will never have the opportunity to use.