I agree that the quatrains are cryptic, and that they seem so vague that anything could be 'predicted' with them
But it's not so, at least in this case, anyway.
These quatrains cannot be properly, legitimately interpreted in any other way...
The Sun, hidden, eclipsed by Mercury.
This 'Sun' is described as being 'placed only second in the skies' (or 'heavens').
So we know this 'Sun' is in the skies. And so is 'Mercury'.
It cannot be more clear on that.
The whole quatrain has to hold up, as well. Not just part(s) of it.
As it does here.
As all 4 of these quatrains do.
While the plant Mercury is at times between the planet Earth and the Sun, Mercury cannot eclipse the Sun.