The impeachment of Andrew Johnson, 5 March 1868, (1872).The Constitution of the United States of America

AMENDMENT XXV  –  Section 4.

Whenever the parties of the VP*
transmit to the parties of Congress*
their declaration that the President is disabled*,
the Vice President shall immediately
assume the office as Acting President.

Thereafter, when the President
transmits to the parties of Congress*
his declaration that no inability exists,
he shall resume his office
unless the parties of the VP*, within four days
transmit to the parties of Congress*
a second declaration that the President is disabled*.

Thereupon Congress shall decide the issue,
assembling within 48 hours.
If the Congress, within 21 days
determines by two-thirds vote of both Houses
that the President is disabled,
the VP shall continue as Acting President;
otherwise, the President shall resume his duties.

The parties of the VP*
the Vice President and a majority of either
the principal officers of the executive departments
or of such other body as Congress may by law provide,
The parties of Congress*
President pro tempore of the Senate
and the Speaker of the House of Representatives
unable to discharge the powers and duties of his office

Passed by Congress July 6, 1965.
Ratified February 10, 1967.