George Washington, "Account of the Battle of Monmouth" (1778) from George Washington: Writings:
George Washington's account of the Battle of Monmouth for Congress has a very dry tone: we did X, they did Y; because we had to march fast I told the men not to carry their Zs; etc. The headnote at the LoA site makes the connection between Washington's dry factual account and his self-control and privateness.
Where Washington most departs from "just the facts, ma'am" is when (a) he comments on how everyone was brave--which is a dry moment with very little in the way of example or evidence; and (b) he comments on the up-coming court-martial of General Lee--or as Washington puts it, his "peculiar Situation."
Apparently, other eye-witnesses of the engagement make a lot of Washington's bravery--he fought on after his horse was shot out from under him. He also was supposed to have lost his temper at General Lee and cursed tremendously. I only wish that had made into his otherwise dry report.
It's so dry, there's not really even enough tone in here to use this as a good source of period-writing style.