capable of proof

References in classic literature ?
He believed secretly and rather defiantly, for it was a fact not capable of proof, that there was something very remarkable about his family.
Lothario then went on to say, "It seems to me, Anselmo, that thine is just now the temper of mind which is always that of the Moors, who can never be brought to see the error of their creed by quotations from the Holy Scriptures, or by reasons which depend upon the examination of the understanding or are founded upon the articles of faith, but must have examples that are palpable, easy, intelligible, capable of proof, not admitting of doubt, with mathematical demonstrations that cannot be denied, like, 'If equals be taken from equals, the remainders are equal:' and if they do not understand this in words, and indeed they do not, it has to be shown to them with the hands, and put before their eyes, and even with all this no one succeeds in convincing them of the truth of our holy religion.
and has distinctly done so in one instance, capable of proof by me.