From a 1975 Reason interview with Ronald Reagan.
And from the WSJ (registration required):
When Mr. Reagan took office, the top marginal U.S. tax rate was 70%. When he left the top rate was 28%; it is now 35%, and even John Kerry has conceded with his proposal to cut some corporate taxes that the marginal rate of tax matters. Today Americans may disagree about what tax cuts are needed, how deep they should go, and what they ought to target. But the debate itself reflects Mr. Reagan's central premise: that people respond to incentives, and that high taxes interfere with natural human creativity and drive.
Meanwhile, Jesse Walker gives Reagan mixed marks.