from
Bouvier's Law Dictionary, Revised 6th Ed (1856)
MEMBER OF CONGRESS. A member of the senate or house of representatives of
the United States.
2. During the session of congress they are privileged from arrest,
except for treason, felony, or breach of the peace; they receive a
compensation of eight dollars per day while in session, besides mileage.
(q.v.)
3. They are authorized to frank letters and receive them free of
postage for sixty days before, during, and for sixty days after the session.
4. They are prohibited from entering into any contracts with the United
States, directly or indirectly, in whole or in part for themselves and
others, under the penalty of three thousand dollars. Act of April 21, 1808,
2 Story's L. U. S. 1091. Vide Congress; Frank.