Irving Fisher (1867-1947) was one of the greatest and clearest-thinking economists of all time.  He established the theoretical support for modern discounted cash flow analysis, writing that “the value of capital is the present value of the flow of (net) income that the asset generates.”

But he also had other claims to fame … some noteworthy, some less worthy.  In his early 30’s he was stricken with tuberculosis and developed an interest in health.  He wrote a book on How to Live: Rules for Healthful Living Based on Modern Science —ideas he put into practice and proved by living until age 80.  He invented and patented the “visible card index” system in a company which eventually became Remington Rand, making a lot of money in the process (how many economists can say that!).  But despite his brilliant theoretical economics he was less successful in application—he lost most of his wealth in the stock market crash of 1929, and then more through the Great Depression by continuing to insist that recovery was imminent!