Claude Hopkins was one of the greatest advertising pioneers who ever lived.
He believed that "Advertising is salesmanship" and as such, it should be measurable and justify the results that it produced. Claude was a strong believer in "Reason why copy" and the principles that he discovered and documented are as true to day, as then. It does not matter what type of advertising medium you use, from print advertising to the Internet, the fundamental taught by Claude are universal and timeless. He believed, that a good product was often it's own best salesperson and as such he was a great believer in sampling. To help trace his results he would often uses coupons. Coupons gave him the ability to not only measure results, but feedback on how to improve results.