Original meaning
Originalists of all stripes cite "The Federalist Papers". It is fairly tenuous to suggest that this represents a good source for the original "intent": after all, Alexander Hamilton, who wrote the majority of those essays, was absent for the greater part of the Philadelphia Convention, and John Jay did not attend it at all. However, James Madison, the principal framer of the Constitution also wrote a substantial amount of "The Federalist Papers". Also, to suggest Hamilton and Jay's absence from the convention implies their ignorance as to the Constitution's original meaning is demeaning to those two men and inaccurate. The collected anti-Federalist papers, of course, will be no use at all to a person searching for the original "intent" of the framers. However, as evidence of how a reasonable person at the time would have understood the words of the Constitution, "The Federalist Papers" and the anti-Federalist essays are evidence of direct relevance.
Federalism in the United States
The most forceful defense of the new Constitution was "The Federalist Papers", a compilation of 85 anonymous essays published in New York City to convince the people of the state to vote for ratification. These articles, written by Alexander Hamilton and James Madison, with some contributed by John Jay, examined the benefits of the new, proposed Constitution, and analyzed the political theory and function behind the various articles of the Constitution. "The Federalist Papers" remain one of the most important sets of documents in American history and political science.