Palo santo's traditional use predates any documentation checked so far, and no specific dated colonial era or archaeological source naming it has been located.
What would resolve this An ethnohistorical study of early colonial Spanish accounts of coastal Ecuadorian and Peruvian ritual practice, or an archaeobotanical identification of Bursera graveolens residue from a securely dated find.
OpenEthnohistory, archaeobotanyMircea Eliade (ed.); Lindsay Jones (ed., 2nd ed.), Encyclopedia of Religion