Not true I have had white seeds sprout before that were really premature. The only way to tell if a seed is good is to germinate it. I never got where this came from.
Why would your fingers mushing a seed be a good way to tell if it is viable?
Good question. Its probably a good way to render a seed NON-viable!
I think the question here is, "Short of trying to germinate it, is there any good way to determine if a seed is viable"?
I think the answer to that is "no".
Clues that indicate that a seed may be viable include: Maturity (dark color, stripes, large size) and intact shell, but these things aren't absolute. Small seeds and immature ones can still germinate, and of course perfect looking seeds that have been stored badly and are old may not.