Pacioli's historic treatise on double-entry bookkeeping, published in 1494, entitled "Particularis de computis et scripturis" ("Details of Computation and Recording"), is probably the first published book on double-entry bookkeeping, a historic document and a bestseller at its time printed on the Gutenberg press, providing a detailed description of the Venetian system of accounting. The treatise is contained in his larger work "Summa de arithmetica, geometria, proportioni et propor-tionalita". "Pacioli's important manuscript made him instantly famous, and he was invited to Milan to teach mathematics at the Court of Duke Lodovico Maria Sforzo in Milan. One of his pupils would be Leonardo da Vinci (1452-1519). During the seven years Pacioli and da Vinci spent together, the two would help each other create two masterpieces that would withstand the test of time. Da Vinci illustrated Pacioli's next and second most important manuscript De Divina Proportione ("Of Divine Proportions") published in 1509. Pacioli taught da Vinci perspective and proportionality. This knowledge allowed da Vinci to create one of his greatest masterpieces, a mural on the north wall of the Santa Maria de Gracia Dominican cloister. This mural is the most famous painting of the fifteenth century, known as "The Last Supper." The geometry Pacioli taught da Vinci would occur in many of da Vinci's later works. Da Vinci mentions Pacioli many times in his notes." "It is not at all surprising to find a treatise of mercantile procedures in a book on mathematics. At the time, mercantile arithmetic was an established part of mathematics, and its teachers were mathematicians." Prior to its first publication in 1494, Pacioli had been working on the Summa de Arithmetica for some thirty years. He felt that his teaching had fallen to a low ebb and thought that the shortcoming lay in the use of improper methods and in the scarcity of available literature. Pacioli sought to correct these faults in the Summa which is divided into the following parts: 1. Arithmetic and algebra. 2. Their use in trade reckoning. 3. Bookkeeping. 4. Money and exchange. 5. Pure and especially applied geometry. The 'novelty' of double-entry bookkeeping is that all business transactions are recorded in a systematic self-balancing way consisting of the debit(s) (dee dare—shall give) and the credit(s) (dee avere or havere―shall have). After the merchant takes his inventory of all of his possessions, and all of his debts, he uses