The "third man" mirage was considered a mountain mystery by some early
Alpine and Himalayan climbers. It is described in various accounts of
climbs of the time,
including that of Whymper's tragic attempt on the Matterhorn.
In his footnotes to "The Waste Land", T.S. Eliot glosses the lines:
Who is the third who walks always beside you?
When I count,
there are only you and I together
But when I look ahead up the white
road
There is always another one walking beside you
with:
"The following lines were stimulated by the account of one of the Antarctic expeditions (I forget which, but I think one of Shackleton's): it was related that the party of explorers, at the extremity of their strength, had the constant delusion that there was one more member than could actually be counted." (From the internet).
At first I thought this might merely be another example of Eliot's
intermittent sloppiness, but then I found: "Shackleton, for his part, attributed
their astonishing success to something else: 'I know that during that long and
racking march of 36 hours over the unnamed mountains and glaciers of South
Georgia, it seemed to me often that we were four, not three.' [against-the-day.pynchonwiki.com/