Lyndon Johnson actually said...
The authority vested in the President by Section 3 of the Travel Expense Act of 1949, 63 Stat. 166 (5 U.S.C. 836), to establish maximum rates of per diem allowances for civilian officers and employees of the Government to the extent that such authority pertains to travel status of such officers and employees while en route to, from, or between localities situated outside the 48 contiguous states of the United States and the District of Columbia.
08/03/1966