There's a Hawaiian version too.
One one could test it.
So, as tradition says:
If you dig a hole on the waxing moon, you'll have too much dirt left over to refill the hole.
If you dig a hole on the waning moon, you'll not have enough.
Having tried it, I think it's bunk, but go for it. Take a test over a 2 month period.
That has nothing to do with dowsing. I studied that for a couple of years while getting a degree in epistemology, of all damn things. . .
So, do we know what we know we know? I really doubt it. That's the problem, mostly. The remedy? Know what you know, and what you don't, and fix what you don't. That can take time.