He had ranched in the Dakotas, stalked cougars in Arizona, and trekked across the Sahara, but there was still so much left to explore. That’s why, as a spry 55 year old, he formed a small expedition to travel an uncharted tributary of the Amazon, known to Europeans as El Rio da Dúvida (the River of Doubt). Cotton khakis were the only trouser for the job. Ours are like his. Plain front, reinforced knees, stain and wrinkle resistant, and breathable. Wear them long enough, and they might name a river after you.