Article 1, Section 8, Clause 6
Document 1
Records of the Federal Convention
[2:315; Madison, 17 Aug.]
Mr. Governr Morris thought it would be necessary to extend the authority farther, so as to provide for the punishment of counterfeiting in general. Bills of exchange for example might be forged in one State and carried into another:
It was suggested by some other member that foreign paper might be counterfeited by Citizens; and that it might be politic to provide national authority for the punishment of it. . . .
Mr. Elseworth enlarged the motion so as to read "to define and punish piracies and felonies committed on the high seas, counterfeiting the securities and current coin of the U. States, and offences agst. the law of Nations" which was agreed to, nem. con.
The Founders' Constitution
Volume 3, Article 1, Section 8, Clause 6, Document 1
http://press-pubs.uchicago.edu/founders/documents/a1_8_6s1.html
The University of Chicago Press
Farrand, Max, ed. The Records of the Federal Convention of 1787. Rev. ed. 4 vols. New Haven and London: Yale University Press, 1937.