Article 3, Section 3, Clauses 1 and 2
Document 2
Sir Edward Coke, Third Institute 38
1641By this act [3 Henry VII] it expressly appeareth by the judgement of the whole Parliament, that besides the confederacy, compassing, conspiracy, or imagination, there must be some other overt act or deed tending thereunto, to make it treason within the statute of 25 E. 3. And therefore the bare confederacy, compassing, conspiracy, or imaginations by words only, is made felony by this Act. But if the Conspirators do provide any weapon, or other thing, to accomplish their devilish intent, this and the like is an overt act to make it treason.
The Founders' Constitution
Volume 4, Article 3, Section 3, Clauses 1 and 2, Document 2
http://press-pubs.uchicago.edu/founders/documents/a3_3_1-2s2.html
The University of Chicago Press