It is commonly[1,2] held that Simon Stevin invented the decimal number system with decimal point (at least in Europe) in his 1585 book De Thiende. However, in della Porta's book Magia Naturalis, Book 17, Chapter 16, there is a clear reference to a decimal point as 360.0.0.0. You can see the 1658 English translation here and the 1619 Latin version. I do not have access to the original 1558 version. Are these post factum additions of the 17th century (possibly by della Porta himself) or is it truly an anticipation of the decimal system?

[1] J.T. Derrese, G Varden Berghe, "The Wonderful World of Simon Stevin" Chapter 3; page 58: "It is clear that Stevin regarded De Thiende as his own invention and that he was very proud of it."

[2] Dirk Jan Struik, "A Source Book in Mathematics, 1200-1800", page 7, "The introduction of decimal fractions as a common computational practice can be dated back to the Flemish pamphlet De Thiende"

It is commonly[1,2] held that Simon Stevin introduced the decimal number system with the decimal point (at least in Europe) in his 1585 book De Thiende. However, in della Porta's book Magia Naturalis, Book 17, Chapter 16, there is a clear reference to a decimal point as 360.0.0.0. You can see the 1658 English translation here and the 1619 Latin version. I do not have access to the original 1558 version. Are these post factum additions of the 17th century (possibly by della Porta himself) or is it truly an anticipation of the decimal system?

[1] J.T. Derrese, G Varden Berghe, "The Wonderful World of Simon Stevin" Chapter 3; page 58: "It is clear that Stevin regarded De Thiende as his own invention and that he was very proud of it."

[2] Dirk Jan Struik, "A Source Book in Mathematics, 1200-1800", page 7, "The introduction of decimal fractions as a common computational practice can be dated back to the Flemish pamphlet De Thiende"

It is commonly held that Simon Stevin invented the decimal number system (at least in Europe) in his 1585 book De Thiende. However, in della Porta's book Magia Naturalis, Book 17, Chapter 16, there is a clear reference to decimals as 360.0.0.0. You can see the 1658 English translation here and the 1619 Latin version. I do not have access to the original 1558 version. Are these post factum additions of the 17th century (possibly by della Porta himself) or is it truly an anticipation of the decimal system?

It is commonly[1,2] held that Simon Stevin invented the decimal number system with decimal point (at least in Europe) in his 1585 book De Thiende. However, in della Porta's book Magia Naturalis, Book 17, Chapter 16, there is a clear reference to a decimal point as 360.0.0.0. You can see the 1658 English translation here and the 1619 Latin version. I do not have access to the original 1558 version. Are these post factum additions of the 17th century (possibly by della Porta himself) or is it truly an anticipation of the decimal system?

[1] J.T. Derrese, G Varden Berghe, "The Wonderful World of Simon Stevin" Chapter 3; page 58: "It is clear that Stevin regarded De Thiende as his own invention and that he was very proud of it."

[2] Dirk Jan Struik, "A Source Book in Mathematics, 1200-1800", page 7, "The introduction of decimal fractions as a common computational practice can be dated back to the Flemish pamphlet De Thiende"