1. Not all votes of the members present need be recorded in the official journal.
"...the Yeas and Nays of the Members of either House on any question shall, at the Desire of one fifth of those Present, be entered on the Journal." In other words, if less than one-fifth want to include the actual votes then they are left out of the official record.
2. Neither House can meet anywhere different without agreement
"Neither House, during the Session of Congress, shall, without the Consent of the other, adjourn for more than three days, nor to any other Place than that in which the two Houses shall be sitting."
3. A Congressman cannot be arrested for misdemeanors on the way to the Hill
"[Senators and Representatives] shall in all Cases, except Treason, Felony and Breach of the Peace, be privileged from Arrest during their Attendance at the Session of their respective Houses, and in going to and returning from the same...."
4. Congressmen shall not be questioned for speeches in either House
"...and for any Speech or Debate in either House, [Congressmen] shall not be questioned in any other Place." I wonder how many Congressmen have used that defense on CNN or Fox News.
5. No one can be convicted of treason without two witnesses or confession
"No Person shall be convicted of Treason unless on the Testimony of two Witnesses to the same overt Act, or on Confession in open Court." One person is not enough.
6. The President can adjourn Congress
"[The President] may, on extraordinary Occasions, convene both Houses, or either of them, and in Case of Disagreement between them, with Respect to the Time of Adjournment, he may adjourn them to such Time as he shall think proper." While many people know that the president can call a special session of Congress, it is less well known that he can actually adjuorn them if they disagree about when they want to adjourn.