1848: Exposure to the Sun

"There are few points which seem less generally understood, or more clearly proved, than the fact that exposure to the sun, without exercise sufficient to create free perspiration, will produce illness; and that the same exposure to the sun, with sufficient exercise, will not produce illness. Let any man sleep in the sun, he will wake perspiring and very ill; perhaps he will die.--Let the same man dig in the sun for the same length of time, and he will perspire ten times as much, and be quite well. The fact is, that not only the direct rays of the sun, but the heat of the atmosphere produce abundance of bile, and powerful exercise alone will carry off that bile."

~From Texas Presbyterian. (Houston, Tex.), March 11, 1848