Federalist 66: 14
The security essentially intended by the Constitution against corruption and treachery in the formation of treaties, is to be sought for in the numbers and characters of those who are to make them. The JOINT AGENCY of the Chief Magistrate of the Union, and of two thirds of the members of a body selected by the collective wisdom of the legislatures of the several States, is designed to be the pledge for the fidelity of the national councils in this particular. The convention might with propriety have meditated the punishment of the Executive, for a deviation from the instructions of the Senate, or a want of integrity in the conduct of the negotiations committed to him; they might also have had in view the punishment of a few leading individuals in the Senate, who should have prostituted their influence in that body as the mercenary instruments of foreign corruption: but they could not, with more or with equal propriety, have contemplated the impeachment and punishment of two thirds of the Senate, consenting to an improper treaty, than of a majority of that or of the other branch of the national legislature, consenting to a pernicious or unconstitutional law, a principle which, I believe, has never been admitted into any government. How, in fact, could a majority in the House of Representatives impeach themselves? Not better, it is evident, than two thirds of the Senate might try themselves. And yet what reason is there, that a majority of the House of Representatives, sacrificing the interests of the society by an unjust and tyrannical act of legislation, should escape with impunity, more than two thirds of the Senate, sacrificing the same interests in an injurious treaty with a foreign power? The truth is, that in all such cases it is essential to the freedom and to the necessary independence of the deliberations of the body, that the members of it should be exempt from punishment for acts done in a collective capacity; and the security to the society must depend on the care which is taken to confide ...
Article 1 Section 3: 6
The Senate shall have the sole Power to try all Impeachments. When sitting for that Purpose, they shall be on Oath or Affirmation. When the President of the United States is tried, the Chief Justice shall preside: And no Person shall be convicted without the Concurrence of two thirds of the Members present.
Article 1 Section 7: 2
... it. If after such Reconsideration two thirds of that House shall agree to pass the Bill, it shall be sent, together with the Objections, to the other House, by which it shall likewise be reconsidered, and if approved by two thirds of that House, it shall become a Law. But in all such Cases the Votes of both Houses shall be determined by yeas and Nays, and the Names of the Persons voting for and against the Bill shall be entered on the Journal of each House respectively. If any Bill shall not be returned by the President within ten Days (Sundays excepted) after ...
Article 1 Section 7: 3
... which the Concurrence of the Senate and House of Representatives may be necessary (except on a question of Adjournment) shall be presented to the President of the United States; and before the Same shall take Effect, shall be approved by him, or being disapproved by him, shall be repassed by two thirds of the Senate and House of Representatives, according to the Rules and Limitations prescribed in the Case of a Bill.
Article 1 Section 10: 3
No State shall, without the Consent of Congress, lay any Duty of Tonnage, keep Troops, or Ships of War in time of Peace, enter into any Agreement or Compact with another State, or with a foreign Power, or engage in War, unless actually invaded, or in such imminent Danger as will not admit of delay.
Article 5: 1
The Congress, whenever two thirds of both Houses shall deem it necessary, shall propose Amendments to this Constitution, or, on the Application of the Legislatures of two thirds of the several States, shall call a Convention for proposing Amendments, which, in either Case, shall be valid to all Intents and Purposes, as Part of this Constitution, when ratified by the Legislatures of three fourths of the several States, or by Conventions in three fourths thereof, as the one or the other Mode of Ratification may be proposed by the Congress; Provided that no Amendment which may be made prior to the Year One thousand eight hundred and eight shall in any Manner affect the first and fourth Clauses ...
Amendment 12: 1
... Vice President, shall be the Vice President, if such number be a majority of the whole number of Electors appointed, and if no person have a majority, then from the two highest numbers on the list, the Senate shall choose the Vice President; a quorum for the purpose shall consist of two thirds of the whole number of Senators, and a majority of the whole number shall be necessary to a choice. But no person constitutionally ineligible to the office of President shall be eligible to that of Vice President of the United States.
Amendment 18 Section 3: 1
[This article shall be inoperative unless it shall have been ratified as an amendment to the Constitution by the legislatures of the several States, as provided in the Constitution, within seven years from the date of the submission here of to the States by the Congress.]
Amendment 20 Section 6: 1
This article shall be inoperative unless it shall have been ratified as an amendment to the Constitution by the legislatures of three-fourths of the several States within seven years from the date of its submission.
Amendment 22 Section 2: 1
This article shall be inoperative unless it shall have been ratified as an amendment to the Constitution by the legislatures of threefourths of the several States within seven years from the date of its submission to the States by the Congress.