The newspaper advertisement for volunteers to accompany Ernest Shackleton on his planned traverse of Antarctica in 1914 was frank in its offering. "Men wanted for hazardous journey. Low wages, bitter cold, long hours of complete darkness. Safe return doubtful. Honour and recognition in event of success." Still, hundreds applied. There were few chances left to be the first to reach the last challenge on Earth. As the 20th Century came of age, explorers...