You'd have to chew about thirty leaves to get the desired effect according to certain web-sources. If they're dried, this is probably the size of a small lighter, if not, it's too big for your mouth. Smoking is probably easier, as the taste is quite foul and you need to chew for half an hour. The effects are much stronger when smoked as well, as more of the Salvinorin is taken in through the lungs than sublingually. The effects last shorter while smoked, though, so you could try to make it last longer by chewing the leaves.