Charles Hose & William Mcdougall 
Borneo shamanism [EPUB ebook] 

‘…The Kayans dislike and discourage all magical practices, with the exception of those which are publicly practised for beneficent purposes and have the sanction of custom.
In the old days they used to kill those suspected of working any evil by magic. There are no recognised magicians among them other than the DAYONGS, and these, as we have seen, perform the functions of the priest and the physician rather than those OF the wizard or sorcerer.
Some of the DAYONGS make use at certain ceremonies of a rough mask carved out OF wood, or made from the shell of a gourd. The mask is merely an oval shell with slits for eyes and mouth, generally blackened with age and use. It may be worn during the soul-catching ceremony, but not during attendance on the recently deceased. This use of a mask is not known to us among any other of the peoples…’