How was Macbeth duped by the first apparition?

The apparitions came out of the Witches Brew , so, in a sense were hallucinations. In the movie directed by Polanski, the war lord of the title- DRANK the entire concoction in on gulp and then saw things coming out of the cauldron, which oddly seemed to be about the size of the Liberty Bell. The business about the Dagger of the Mind is certainly redolent to Drug abuse - and the Manson Murders.