To the Senate and House of Representatives of the United States:
I communicate to Congress certain letters which passed between the British secretary of state, Mr. Canning, and Mr. Pinkney, our minister plenipotentiary at London. When the documents concerning the relations between the United States and Great Britain were laid before Congress at the commencement of the session, the answer of Mr. Pinkney to the letter of Mr. Canning had not been received, and a communication of the latter alone would have accorded neither with propriety nor with the wishes of Mr. Pinkney. When that answer afterwards arrived it was considered that, as what had passed by conversation had been superseded by the written and formal correspondence on the subject, the variance in the two statements of what had verbally passed was not of sufficient importance to be made the matter of a distinct and special communication. The letter of Mr. Canning, however, having lately appeared in print, unaccompanied by that of Mr. Pinkney in reply, and having a tendency to make impressions not warranted by the statements of Mr. Pinkney, it has become proper that the whole should be brought into public view.
Thomas Jefferson, Special Message Online by Gerhard Peters and John T. Woolley, The American Presidency Project https://www.presidency.ucsb.edu/node/203411