Edit: Reading further, it's clearly about the written form used: > [I]t is unlikely that Harriot hit upon binary notation simply because he was using weights i

Edit: Reading further, it's clearly about the written form used: > [I]t is unlikely that Harriot hit upon binary notation simply because he was using weights in a power-of-2 ratio, something that was a well-established practice at the time. Equally if not more important was the fact that he recorded the measurements made with these weights in a power-of-2 ratio too. For when recording the weights of the various part-ounce measures, Harriot used a rudimentary form of positional notation, in which for every position he put down either the full place value or 0, depending on whether or not the weight in question had been used. My original comment: I'm a little unclear, as the article mentions "binary numeration" several times. Am I to understand that the Harriot is the first written evidence of binary in a modern form, that is, using arabic numerals like we do today? (example we'd write four as: 100) Other commenters are noting that base 2 has been known for far longer than the last 500 years.