US Constitution Series, Article I, Section 5

Article I. LEGISLATIVE DEPARTMENT

§ 5. Powers and Duties of the Houses

Each House shall be the Judge of the Elections, Returns and Qualifications of its own Members, and a Majority of each shall constitute a Quorum to do Business; but a smaller Number may adjourn from day to day, and may be authorized to compel the Attendance of absent Members, in such Manner, and under such Penalties as each House may provide.

Each House may determine the Rules of its Proceedings, punish its Members for disorderly Behaviour, and, with the Concurrence of two thirds, expel a Member.

Each House shall keep a Journal of its Proceedings, and from time to time publish the same, excepting such Parts as may in their Judgment require Secrecy; and 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.

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.

There are a number of interesting things in this article:

1. For each House, a majority must be present to vote on anything, which is the official conduct of business. We see speeches on C-span where members are speaking to essentially an empty room. speeches are not the conduct of business, votes are.
2. Each house may expel members, but it takes a two-thirds vote. Only 20 members have been expelled, mostly Southern sympathizers during the Civil War.
3. A house may not adjourn for more than three days without the consent of the other and they must meet in close physical proximity.