Where Did Chief Joseph Get His Mesopotamian Tablet?
I answered the title question on Facebook:
Brought from the Old World a few decades earlier as a souvenir; traded or lost until it reached Joseph. Not proof that ancient Sumerians visited America. That's my theory, anyway.
This led to the following debate with "Rick":
Earlier is possible too
Sure, some Vikings or other pre-Columbian explorers could've brought the tablet with them. This still contradicts the implied claim that ancient Sumerians visited America. There's no reason to believe this theory except an unreliable interpretation of Joseph's vague words.
Sumerians wouldn't have visited America and left zero archaeological evidence except one tablet. A cross-country expedition that reached Idaho or wherever should've left several traces.
All this is speculation based on some white man's interpretation of Joseph's words "long ago." (Is that a direct quote or a paraphrase? Who knows?) It could refer to 3,000 years ago, or to 100 years ago. We simply don't know.
Without further evidence, I'm going with the simplest explanation. I.e., mine. <g>
To sum it up, any pre- or post-Columbian explorer could've brought the tablet to Joseph's ancestors. Someone visiting a couple of centuries before Joseph's time seems most likely to me.
For another claim about a non-Sumerian explorer, see New Films on Prince Madoc.