Lyndon Johnson actually said...
The policies and practices should be based upon the principles that (1) wages shall be fixed and adjusted from time to time as nearly as is consistent with the public interest in accordance with prevailing rates, and (2) there shall be equal pay for substantially equal work, and pay distinctions shall be maintained in keeping with work distinctions.
Context
Memorandums on the Need for Coordinating the Practices of Federal Wage Boards
11/15/1965