Y I N Y A N G
Long considered the universal sign of balance, the Yin & Yang is one of the oldest symbols in the various books. In fact, it was known even before books were a thing! To me it is also the symbol of the Law of Attraction, a concept some people say does not work, but my experience tells me differently!
Actually, my own experience with the Yin & Yang was started around the turn of the last millennium, when I went through an intuitive drawing session lasting around three weeks. The end result was the SevenSphere on the right here, which basically became the tool of choice through which I saw my reality.