Bill Gates is up there. So are William the Conquerer, a czar, assorted nobility and a smattering of Rockefellers, Carnegies and Vanderbilts. But even at the peak of their considerable wealth, none surpassed the riches of the most moneyed man ever: Mansa Musa I, a West African king who died in 1337. That’s according to a list of the 25 most well-off men – yep, it’s an all-boys club – to have ever walked the planet, according to Celebritynetworth.com. The site took the high-point estimate of each man’s net worth and adjusted the fortunes for inflation. In total, the group held more than $4.3 trillion. Fourteen of the 25 were Americans – with Microsoft founder Bill Gates as the richest living member. Carlos Slim Helu, currently the richest person worldwide, came in 22nd. Billionaire investor and Berkshire Hathaway chief Warren Buffett rounded out the list with $64 billion, closely following Wal-Mart founder Sam Walton’s $65 billion.