Most navigators have heard of Viking sunstones, but few realize they are more than legend. Leif Karlsen has brought them to life. He shows us how they work—now, and a thousand years ago—and what it was that led the Viking navigators to develop this unique tool for finding the direction to the sun, even when the sun is obscured by clouds or fog. | Secrets of the Viking Navigators by Leif K Karlsen, Paperback | Indigo Chapters