2D picture with relief: how to select deep ends?

[Xogroroth]

Hail all:

I have a 2D picture with relief (see photo), I am trying to select the whole carved out part, no luck.

Tried to enhance the edges (sharpen and High Pass) to bring out the edges, retry ... nothing.
The sharpened picture then, I too though the Photocopy, hoping to get a clean edge around ... no ball.
Black and white, and combinations of the above steps, none succeed.

Been looking in Google for a solution, though, no luck there either.
YouTube?
Nada.

Tried alternative search engines (Yahoo for one), nope no luck.

Is there anyone here that can help me, please?

Thank you.