Links to images of William Niven Tablets from the Peabody Museum at Harvard:
http://blog.my-mu.com/?p=2458
http://blog.my-mu.com/?p=2465
http://blog.my-mu.com/?p=2470
Jeb Card and the Mu Stones Pt I on the ArchyFantasies Podcast.
Here are recently obtained images of Niven’s tablets from the Valley of Mexico:
An outline of the symbol on the Mu Stone shown in the video is here.
The video: