We do not belong to those who have ideas only among books, when stimulated by books. It is our habit to think outdoors — walking, leaping, climbing.

— Friedrich Nietzsche, surfaced by Maria Popova. Half-blind and bedridden by migraines in his thirties, he found one remedy: walking one hour each morning and three each afternoon, later up to ten a day, composing The Wanderer and His Shadow almost entirely on foot.