I've gotten hold of one of those fab retro orange Penguin books and been reading South by Ernest Shackleton. I'm loving the mirage descriptions:
"At the same time the ice cliffs of the land were thrown up in the sky by mirage, with an apparent reflection in open water, though the land itself could not be seen definitely. The effect was repeated in an exaggerated form the following day, when the ice cliffs were thrown up above the horizon in double and treble parallel lines, some inverted...
Bergs and pack are thrown up in the sky and distorted into the most fantastic shapes. they climb, trembling, upwards, spreading out into long lines at different levels, then contract and fall down leaving nothing but an uncertain wavering smudge which comes and goes. Presently the smudge swells and grows, taking shape until it presents the perfect inverted reflection of a berg on the horizon. These spread out into lines until they meet, and are girdled by lines of shining snow cliffs, laved at their bases by waters of illusion in which they appear to be faithfully reflected.
So the shadows come and go silently, melting away finally as the sun declines to the west. We seem to be drifting helplessly in a strange world of unreality."