Sweetgrass's ceremonial use is a living Indigenous North American tradition, and no specific, dated, non-intrusive documentary or archaeological source establishing its earliest attested use has been located.
What would resolve this An archaeobotanical study identifying Hierochloe residue from a securely dated site, or a documented early written account naming the practice without describing closed ceremonial content.
OpenArchaeobotany, ethnohistoryMircea Eliade (ed.); Lindsay Jones (ed., 2nd ed.), Encyclopedia of Religion