'In 1951 Sen Tensing, Shipton, and I descended from the Menlung La ... at about 16,000-17,000 feet we came across a whole series of footprints in the snow, on the lower part of the glacier. There seemed to be two groups, one rather indistinct in outline leading on to the surrounding snowfields. The others were much more distinct with, in places, a markedly individual imprint etched in the 2- to 4-inch covering of snow. We had no means of measuring so after examining them Shipton took four photographs: two of the indistinct prints with myself, my footprints, and rucsac beside them for comparison; the other two photographs were of one of the most detailed and distinct group of prints, with my ice axe for scale, and a second one with my booted foot. The footprint was about the same length as my boot, and I take a size 42 continental, or 8½ British, which is about 12 to 13 inches long. The print was nearly twice as broad as my boot (3 to 4 inches) and had clear-cut edges in the crystalline snow on a base of firm snow ice. There was the definite imprint of a big toe that was broader and shorter than the other rather indistinct toes, of which there seemed to be four or five. We followed these tracks for some way down the easy glacier and noticed that whenever a narrow 6-inch-wide crevasse was crossed there seemed to be claw marks in the snow at the end of the toe imprints. ... Two days later we were joined by Murray and Bourdillon, who, after visiting the Nangpa La ... had followed our route into the Menlung Basin. All tracks had been deformed by the sun and wind.' (Michael Ward, 'Everest 1951: the footprints attributed to the Yeti -- myth and reality', Wilderness and Environmental Medicine, 8, 29-32 (1997)).
Shipton's photographs ignited speculation about the existence of a Yeti which had been growing since N.A. Tombazi made the first European sighting during an expedition to the Sikkim Himalaya in 1925.
Edmund Hillary had a further encounter in 1952 on a pass between the Ngojumba and Khumbu glaciers: 'We were climbing quite a steep pitch when Pemba stopped and picked something off the rock. Obviously greatly excited, he showed it to Angpemba. Feeling somwhat curious, I asked them what it was all about. They placed in my hand a tuft of long black hairs -- thick and coarse, they looked more like bristles than anything else. "Yeti, Sahib! Yeti!" I couldn't help being impressed by their conviction, and it did seem a strange place to find some hair. We were well over 19,000 feet and the Abominable Snowman was obviously no mean rock climber' (Hillary, High Adventure, 1955, p. 103).
Following these various incidents, Hillary mounted an expedition in 1960 to collect and evaluate evidence of the Yeti, with inconclusive results. British mountaineer Don Whillans was a fervent believer, claiming he encountered the Yeti while scaling Annapurna in 1970. He observed a few human-like footprints in the snow around his camp one morning and, that evening, claimed that through binoculars he watched a bipedal, ape-like creature for about 20 minutes as it apparently searched for food not far from his camp.