Just in case you're thinking of doing this; I must tell you, it is beyond scary. The trip induced by smoking salvia divinorum extract is often an intensely terrifying experience that most people do not wish to repeat. There are positive experiences which you can read about, but it's generally accepted to be dysphoric in nature.
Once smoked, the onset is incredibly quick and the nature of this atypical hallucinogen is such that you immediately forget having taken the drug. This situation is highly conducive to confusion and fear when you begin to experience the outrageously bizarre hallucinations, with no available explanation for their cause. The hallucinations tend to involve very physical sensations of being pulled downward in one or more directions and feelings of bodily distortion. The visuals are not typical kaleidoscopic hallucinations but are often rather frighteningly dark and twisted. It's common to experience a strong feeling of presence of people who aren't there, entities may appear in your hallucinations. Quite uniquely, people report with unusually common frequency and consistency, seeing motifs of zippers, arrows, wheels, cogs/sprockets and other repeating patterns.
I've tried it a few times, and one time in particular was unforgettable for all the wrong reasons; I entered a delusional state whereby I was convinced that I had merged bodily with my sofa and would be stuck there until the end of time. It was two minutes of pure unadulterated fear. :D