One monk's 1494 maths textbook invented modern accounting

Venetian merchants had used double-entry bookkeeping informally for over a century, but Franciscan friar Luca Pacioli was the first to write the system down in full, inside a mathematics textbook rather than an accounting manual. His method of recording every transaction as a matched debit and credit made a business's full financial position visible at a glance, and caught errors that single-entry records hid. It's essentially the same system every company's books still run on today.

— Luca Pacioli, Summa de arithmetica, geometria, proportioni et proportionalita — 1494