Simon Stevin Quote
The Rule of Three, or Golden Rule of Arithmetical whole Numbers. Be the three terms given 2 3 4....To finde their fourth proporcional Term: that is to say, in such Reason to the third term 4, as the second term 3, is to the first term.... Multiply the second term 3, by the third term 4, & giveth the product 12: which dividing by the first term 2, giveth the Quotient 6: I say that 6 is the fourth proportional term required.
Disme: the Art of Tenths, Or, Decimall Arithmetike (1608)