The Greek I can't fully translate is in Loeb 249, the intro to Tacitus' Annals, p. 237. "Nor, in any case, is it given to many historians - to none, perhaps, of the greatest - to comply with the precept of Lucian (repeated almost to the letter by Ranke): Tou suggrapheos ergon en, hos epraxthay eipein." For not the most stubborn of facts can pass through the brain of a man of genius, and issue such as they entered..."
Something to the effect, In a work of history let the facts speak...?
I couldn't find the key work, epraxthay - eta-pi-rho-alpha-xi-theta-eta - in the L&S.