How Lewis and Clark's laxative pills help archaeologists find their campsites today

There were, however, some particular pains they were experiencing, as a result of a relentlessly low-fiber diet: Everyone was constipated, all the time.

The Corps of Discovery left on its journey with a trove of 600 giant pills that the men called 'thunder-clappers,' which the soldiers and travelers used to jump-start things when they got bound up.

Archaeologists simply have to search for dimples in the ground — which is what old latrine pits often end up looking like, hundreds of years later, after Nature has partly filled them in — and take samples of the dirt in them.

If it comes up with an off-the-charts reading for mercury, well, that's a Corps of Discovery pit toilet — and the layout of the rest of the campsite can be extrapolated with considerable precision by consulting the military manuals they used to lay out their camps.