“And the throwing of incense was done in this manner: when any kind of speech was to be made, perhaps a sentence to be passed, they first threw incense in the fire. Before a person spoke, there, in a bowl, was the Kopal. Or when a singer was to sing, when he was about to begin, first he threw the Kopal into a brazier. Then the singer began”
Primeros Memoriales
The Mexika Calendar System 