What are the essential elements of possession of a controlled substance?

"The essential elements of possession of a controlled substance are `dominion and control of the substance in a quantity usable for consumption or sale, with knowledge of its presence and of its restricted dangerous drug character. Each of these elements may be established circumstantially.'" (People v. Palaschak (1995) 9 Cal.4th 1236, 1242, 40 Cal.Rptr.2d 722, 893 P.2d 717 (Palaschak).)