Search Loci: Convergence:
Each problem that I solved became a rule which served afterwards to solve other problems.
Discours de la Methode. 1637.
The Grounde of Artes by Robert Recorde
On this page there is an outline of the first dialogue in this book. (Recorde wrote his book in the form of a dialogue between student and master.) This dialogue deals with some of the elements of arithmetic, including the basic operations and the use of the rule of three (or the Golden rule).
A page dealing with various "rules of practice" in arithmetic.