Last year I came down with a cold and found myself browsing through google books. I stumbled over Euler's Elements and was immediately hooked. After reading 100 pages or so in one afternoon I decided to try teach my kids (8 and 10 year old) using Euler's book as their textbook. And so every Saturday morning we would assemble around the kitchen table and go through a couple of paragraphs of Euler's work. Suffice it to say the kids were amazed by what they learned and how (relatively) easy it was for them to follow. Indeed, Euler's clarity of explaining the subject matter is unrivaled - wish the schools would use it. Learning from the masters of a subject, especially when they are gifted to explaining the complicated in clear and lucid terms is a wonderful experience (and reminds me of Hans Oerberg's Lingua Latina).
Fun anecdote: When one of my boys explained to a neighbor kid what imaginary numbers are and how they come about his friend got irritated and said "you are not supposed to know that, you don't even have pi memorized yet"...
Thanks for this great article!