When the sun shone I navigated by means of the...

“When the sun shone I navigated by means of the shadows of a series of penknife-scratched lines on the plastic windshield of my skidoo. To check on the accuracy of this crude system and to put some life back into our frozen limbs, I stopped for five minutes in every hour. We always maintained a space of a mile between each of us so, as soon as I stopped, a backbearing on the two specks back along my trail provided a good check on the angle of travel.”

Mad, Bad and Dangerous to Know by Ranulph Fiennes