1494: how did Luca Pacioli's book spread double-entry bookkeeping?

If a single book introduced an entire profession to the world, it must be the "Summa" printed in Venice in 1494. Curiously, the author openly stated in it that he had invented nothing.

Key facts

1. Who was the author? Luca Pacioli was an Italian mathematician of the Renaissance and a Franciscan friar. According to Britannica Kids, he was born in the town of Borgo San Sepolcro in Tuscany.
2. The book. His work "Summa de arithmetica, geometria, proportioni et proportionalita" was printed in Venice in 1494; it was printed by Paganino de Paganini. In 1523 a second edition appeared in Toscolano, reproducing the first edition page for page.
3. What is in it? The Summa is a large work that brought together the mathematical knowledge accumulated up to that time. A separate section within it explains double-entry bookkeeping in detail and is known as the first printed account of double-entry bookkeeping.
4. Not the inventor. Pacioli did not claim to have devised the method himself. He wrote down the practice used by Italian merchants, especially in Venice, which he called "the method of Venice".
5. Why him in particular? Before him the method was taught orally and through practice in merchant families. Pacioli set it out systematically in a printed book, and the method could now also be learned from a book.
6. Friendship with Leonardo. Pacioli taught in Milan and became friends with Leonardo da Vinci there.
7. "Father of accounting". Because of this book, Pacioli is often called the "father of accounting". A more accurate description: he was the first author to give a systematic printed account of double-entry bookkeeping.

Example: Pacioli's idea in today's chart of accounts (prepared by the author, hypothetical)

The "Zarafshon gilam" shop received carpets worth 18 000 000 soum from a supplier and paid for them later from its bank account. The rule of Pacioli's time, "every transaction on two sides", looks like this today with the accounts of NAS No. 21:

In the first entry goods increased and a debt arose. In the second the debt was settled and the money in the bank decreased. In every line debit and credit are equal: more than five hundred years have passed, but the rule has not changed.