Miley Cyrus Smoking a Bong

The video was shot during a party at Miley’s L.A. area home 5 days after her 18th birthday.

According to a source connected with Miley … the smoke filling the bong is a natural herb called salvia which has psychedelic qualities. Possession of salvia is legal in California.

As for the video … the source tells us it was shot by one of Miley’s friends —  and the theory is someone stole or copied the video from that friend’s camera.