I read a most interesting article on the history of the word Reiki a few months ago. Rather than repeating everything said there I would encourage you to follow the link and read the article for yourself.
We are perhaps most familiar with the first and second images shown here, and I have actually seen debate over which is more correctly used!
Personally, I am drawn to the first image as you can see from the logo I use for my healing practice and for this page.
I think what this shows most importantly though is that it doesn’t really matter which ideogram is used, as long as the intention is present.
Reiki Blog Project – K is for Kanji
- Does “Reiki” work? My Experience With This Healing Technique (redlipstickandcaviar.wordpress.com)
- Writing Reiki