The Records of the Federal Convention of 1787, ed. Max Farrand (New Haven: Yale University Press, 1911). 3 vols. http://oll.libertyfund.org/titles/1785,
A 3 volume collection of the records of the Federal Convention which was held in Philadelphia between May and September 1787. The sessions were secret but the proceedings were reconstructed from notes kept by the official secretary and some participants, most notably James Madison.
The text is in the public domain.