I’m lying in snow, 14,000 feet above sea level on a volcano known as Nevado de Toluca, when I feel warm breath against my hand. Exhale, groan, roll over. It’s a dog, come to investigate my motionless form. “Good dog,” I slur and raise a hand to pat her head. Her name is Maya, I think, and she’s been tagging along with our hiking group since this morning.