7When Napoleon Hill was a young investigative reporter for a business magazine, he was sent to interview the richest man of his time: Andrew Carnegie. During that interview, Carnegie let a comment slip about a 'master power' that he alone uses and that was the foundation for his success and immense wealth. That part of the interview was never published in the magazine, but Napoleon Hill began working on an investigation that was prolonged for more than 25 years studying more than 500 people who had found the most success of the era.