Jules Augustin Frédéric Regnault was a French stock broker's assistant who first suggested a modern theory of stock price changes in Calcul des Chances et Philosophie de la Bourse (1863) and used a random walk model. He is also one of the first authors who tried to create a "stock exchange science" based on a statistical and probabilistic analysis. His hypotheses were used by Louis Bachelier, who is considered a pioneer in the study of financial mathematics. Bachelier had anticipated many of the mathematical results developed in Albert Einstein’s 1905 paper.

In the research paper, Does God practice a random walk? The ‘financial physics’ of a nineteenth-century forerunner, Jules Regnault, Franck Jovanovic and Philippe Le Gall, 2001 said...

"Jules believed that it was the frequency of trades that caused the ruin for the speculator. He referred to it as the law of ruin. Regnault constructed a second model of short-term speculation that incorporated the transaction costs and that enabled him to demonstrate the inexorable ruin of the short-term speculation. Regnault thus had in his hands the elements that could pave the way for a ‘law of ruin’. The chances of loss are increasing with the power of the inverse ratio of time. The frequency of operations is an abuse. The transaction costs represent for him twenty times more, that is 2.5%. As a consequence, since the gain and the loss equilibrates, no more that forty operations will lead to the loss of his capital.”

Simply suggesting this means that lesser the trades the better your portfolio health will be. Jules died on December 9, 1894. When he died, his fortune was estimated at 1,026,510.03 francs (that is more than 3.8 million euros 2004).