I finally took a trip to the Kimbell Art Museum yesterday to see the samurai collection, and I found something of Chrono interest. Beside
this piece was a description saying the helmet was designed to invoke the flaming jewel Cintamani, which is said to have the power to grant wishes. Upon further research, I learned that the Cintamani originates from Hindu and Buddhist teachings, and supposedly fell from the sky.
I thought that was interesting, because this jewel sounds a lot like our Frozen Flame. I wonder if Kato or someone else used it as inspiration.