In Walling v. Portland Terminal Co., 330 U.S. 148 (1947), the Court held that individuals being trained as railroad yard brakemen - individuals who unquestionably worked in 'the kind of activities covered by the Act' - were not 'employees.' The trainees enrolled in a course lasting approximately seven or eight days, during which time they did some actual work under close supervision. If, after completion of the training period, the trainees obtained permanent employment with the railroad, they received a retroactive allowance of four dollars for each day of the course. Otherwise, however, they never received or expected any remuneration. The Court held that, despite the comprehensive nature of the Act's definitions, they were 'obviously not intended to stamp all persons as employees who, without any express or implied compensation agreement, might work for their own advantage on the premises of another.' . . . Considering that the trainees' employment did not 'contemplate . . . compensation,' and accepting the findings that the railroads received ' "no immediate advantage" from any work done by the trainees,' the Court ruled that the trainees did not fall within the definition of 'employee.' "