When you mean 26", do you mean mtn(559 mmERTO), or English Roadster 26" (590mm ERTO)? There is also the 650B (584mm ERTO); the tires for this size are marked 26" also . ERTO refers to the rim, or bead seat diameter. I believe Raliegh made a model called the Portage that came with 650B wheels. There were lots of French touring bikes made for the 650B size, but not a lot of them made it to the US.

A lot of older Mtn bikes make fine tourers because they have braze-ons for cantilevers and racks. Furthermore they are oftn dirt cheap. Many early "mountain" bikes were just beefed up touring bikes with components adapted from touring components. If you go to the Touring sub forum, you can see a thread of mtn bikes adapted for touring.