I greatly approve the epithet which you give, in your letter of the 8th of June, to the new method of treating the small-pox, which you call the tonic or bracing. method; I will take occasion from it to mention a practice to which I have accustomed myself. You know the cold bath has long been in vogue here as a tonic; but the shock of the cold water has always appeared to me, generally speaking, as too violent, and I have found it much more agreeable to my constitution to bathe in another element, I mean cold air. With this view I rise almost every morning, and sit in my chamber without any clothes whatever, half an hour or an hour, according to the season, either reading or writing. This practice is not in the least painful, but, on the contrary, agreeable; and, if I return to bed afterwards, before I dress myself, as sometimes happens, I make a supplement to my night's rest of one or two hours of the most pleasing sleep that can be imagined. I find no ill consequences whatever resulting from it, and that at least it does not injure my health, if it does not in fact contribute much to its preservation. I shall therefore call it for the future a bracing or tonic bath.
Elsewhere Franklin also writes:
In summer-nights, when I court sleep in vain I often get up and sit at the open window or at the foot of my bed, stark-naked for a quarter of an hour. That simple expedient removes the difficulty (whatever its cause), and upon returning to bed I can generally rely upon getting two or three hours of most refreshing sleep.
Let us remember too that Franklin was no mean inventor. Amongst other things he gave us: bifocals, the flexible urinary catheter, the lightning conductor, an especially efficient design of wood-burning stove, the odometer, America's first public library as well as hugely increasing our understanding of electricity and mapping the Gulf Stream. And as if that wasn't enough he was one of the founding fathers of the United States.
Who would doubt the wisdom of such a man?