Hi Alan, long time no see. Glad to "hear" from you.
Years ago, Garry Cundiff took some pics of a cabin on the old home property in Texas where Travis was known to have spent some time growing up. IIRC, they're on Garry's website.
Travis had made some carvings on the stones in the cabin's chimney, and also on a stone that showed a "treasure galleon" with a treasure chest on one side...complete with some "illiterate" wording "en Espanol"
Lots of places for someone who likes to carve to get sandstone

I've always liked the possibility of a quarry that was in existence on RT 66, on Travis' route from Washington to TX. The quarry and yard stacked with thousands of tons of nice, flat sandstone was in existence then, and still is today, and very hard to miss as it's right on the side of the road. And it's even in AZ, Ash Fork to be exact. But who knows where he got it?
There will always be believers that the stones were made by the Jesuits or Spanish/Mexican miners, and that Travis found them buried near Queen Creek. I suppose that's within the realm of possibility.
I've always wondered, if he did carve them, what did he use as a source document? I think the trail maps bear a striking similarity to "LDM maps" attributed to Julia Thomas. But I really have no idea.
Hope all is well with you and yours, Jim