The single most effective step to start getting rich, from a 78-year-old personal finance classic

Nearly a century ago, journalist Napoleon Hill studied over 500 self-made millionaires and boiled down their success into 13 steps.

Their wealth all started with one emotion, he argues: desire.

"Wishing will not bring riches," he writes in "Think and Grow Rich," the culmination of his interviews with Andrew Carnegie, Henry Ford, John D. Rockefeller, and hundreds of other successful people.

"But desiring riches with a state of mind that becomes an obsession, then planning definite ways and means to acquire riches, and backing those plans with persistence which does not recognize failure, will bring riches."

All of the super wealthy started with a certain amount of dreaming, hoping, planning, and desiring before they became rich, Hill writes. They imagined wealth before they saw it in their bank accounts.

This is similar to what Steve Siebold, self-made millionaire and author of "How Rich People Think," preaches today: To be rich, you have to be obsessed with success.

"The truth is wealthy people have a healthy obsession with getting what they want, which includes money," Siebold writes. "If you want to attract more money into your life, think about what you want and what you're willing to sacrifice to get it. Your discipline and dedication must match your desire."

To turn this desire for wealth into "its financial equivalent," Hill outlined the 13 steps anyone can take.