" Amundsen slept with his window wide open at night even in the winter, claiming to his mother that he loved fresh air, but really “it was a part of my hardening process.” He organized small expeditions for himself and a few friends, such as overnight treks on skis under a star-studded sky, enlivened by the otherworldly swirling of the aurora borealis, into the winter wilds to improve his toughness. "

― Stephen R. Bown , The Last Viking: The Life of Roald Amundsen