The St. Louis directory and register :
Section III.

1. Treason against the United States, shall consist only in levying
war against them, or in adhering to their enemies, giving them aid
and comfort. 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.

2. The Congress shall have power to declare the punishment of
treason; but no attainder of treason shall work corruption of blood,
or forfeiture, except during the life of the person attainted.