McConnell Folding Dental Chairs were designed for traveling dentists. 1900

From a vintage ad:

“A stump has some advantages as a Dental Chair in an emergency. It is strong and cheap, but it is heavy and unhandy to move, and would be more convenient and comfortable if it had less attachments and more adjustment. The same might justly be said of the majority of Dental Chairs excepting the high priced ones, and it takes from two to three years to adjust your finances after buying one. ‘THE MCCONNELL’ has none of these defects and all of the advantages, with the additional one that you can fold it up and walk off with it. The best Portable Dental Chair on Earth, and your office is not complete without one or more of ‘The McConnell’ Chairs. The only one in existence that can be elevated and adjusted while occupied.”

Click here for a very detailed history of dentistry.