It's reported that Bob Turley helped Mickey Mantle call pitches in the 1950s. Seems that Turley, when he pitched for the St. Louis Browns earlier in the decade, figured out a way to read an opposing hurler's mannerisms to determine what pitch he was going to throw.
When Turley joined the Yankees for the 1955 season and Mantle found out about his skill, he wanted in.
They developed a system based on Turley whistling. Turley told Mickey to assume the first pitch would be a curve, but if he heard the whistle it would be a fastball. If the pitch after that was another fastball, there would be no whistle. If it were going to be a curve, Turley would whistle again. So the pattern went.
While some opposing pitchers figured out what Turley was doing, no one was ever really able to stop it. The Yankees certainly were fine with the idea: They'd put Turley in a prime stadium seat if he was on the disabled list, and would set him up in a TV studio to study new arms before New York had to face them.
According to Turley, Mantle said half of his 320 home runs from 1955-1962 — the stretch the two played together — came on called pitches.
Whether it's technically cheating is a personal debate, and it isn't the point ... it was about getting an edge. The drug method is certainly a bit more blunt (and a lot less skilled), but this is what professional athletes do.