I suspect what Tom was thinking of was a bit later on. After trekking across the pack ice to Elephant Island, and sailing across the Screaming Sixties to South Georgia in a life boat, there was the small matter of a quick hike across South Georgia. South Georgia is as far south as Britain is north, but it is covered in glaciers. They didn't have crampons, so they worked nails out of the life boat and nailed them into their boots to provide some grip. Shackleton has been my hero for as long as I can remember. I love the saying: "For speed and efficiency, give me Admunsen. For scientific discovery, give me Scott; but when disaster strikes, and all else fails, get down on your knees and pray for Shackleton"