“Hands!” the sergeant barked at me. “Let me see your hands!”

I stuck out my palms, and the sergeant inspected them for calluses. Seeing none, he dismissed me with a grunt. “Yer too green to make the crew. You’d never survive.”

I chafed for an instant. But I knew what he was doing. I had stepped aboard the replica keelboat that was preparing to retrace the journey of Lewis and Clark. The crew, in uniform and in character, were demonstrating their recruiting techniques. They were screening for hardy souls who could withstand two years of pushing boats, hauling gear, hacking brush, plucking ticks and slapping mosquitoes, enduring rain and cold and ice and wet boots, eating bear meat without dipping sauce, and no air conditioning or Big Gulps or laundromats or Cheerios or candy bars or Sirius. The sergeant knew that the trip would be tough, and even intrepid explorers like Meriwether Lewis might crack under the strain. So the sergeant looked for tough.

Calluses.