Mansa Musa, the 14th-century ruler of Mali, is often considered the wealthiest person in recorded history. Here’s what made his fortune so legendary — and how it compares to modern billionaires.

There are many celebrities with a net worth of over a billion, but can you imagine being worth $400 billion (£325 billion)? That's a whole lot of money, and a fortune most people can only dream of, ...