Well, you should see it somewhere on your TV, Radio... many electrical devices bear it. At least where I come from:
http://en.wikipedia.org/wiki/Power_symbol
There is something similar in Reiki it seems:
http://www.hypno-analysis.co.uk/powe...ol%20reiki.gif
But apart from that I can't find much history here. I'm probably not informed about the right terminology.
Some similar signs can be found here:
http://www.radioliberty.com/Symbolsandtheirmeaning.html
Oh actually it's already done:
http://www.empowerthyself.com/symbol