The Spell of the Rockies by Enos A. Mills

I was rambling alone on snowshoes, doing some winter observations in the alpine heights of the Sangre de Cristo range. It was miles to the nearest house. There was but little snow upon the mountains, and, for winter, the day was warm. I was thirsty, and a spring which burst forth among the fragments of petrified wood was more inviting than the water-bottle in my pocket. The water was cool and clear, tasteless and, to all appearances, pure.

As I rose from drinking, a deadly, all-gone feeling overcame me. After a few seconds of this, a violent and prolonged nausea came on. Evidently I had discovered a mineral spring! Perhaps it was arsenic, perhaps some other poison. Poison of some kind it must have been, and poisonous mineral springs are not unknown.