Article 1, Section 9, Clause 5
Document 3
James McHenry, Maryland House of Delegates
29 Nov. 1787Farrand 3:149That no Duties shall be laid on Exports or Tonage, on Vessells bound from one State to another is the effect of that attention to general Equality that governed the deliberations of Convention. Hence unproductive States cannot draw a revenue from productive States into the Public Treasury, nor unproductive States be hampered in their Manufactures to the emolument of others.
The Founders' Constitution
Volume 3, Article 1, Section 9, Clause 5, Document 3
http://press-pubs.uchicago.edu/founders/documents/a1_9_5s3.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.