The question is how large was this snake and hole?
The markers that I have seen that go to treasure locations and weigh many tons such as the Alpha and Omega boulders that were set up on other boulders with no roads going to them certainly were not done within the last 100 years.
Here is a good example this is the Omega Marker.
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This is a nice looking setup. Is this one of the egg shaped markers like Kenworthy shows? So, is the alpha marker the same shape but much bigger? The snake is about ten feet long and the eye is probably 18 inches long and one foot high.