The magician shows four fabric bags standing on the table and explains that each bag is covering a glass and three of them have water, while only one contains poison, a very dangerous poison…
A member of the audience will decide which one has the poison, and the performer promises to drink the contents of the other three glasses.
Then, he asks a spectator to choose the bag he thinks is covering the glass with poison. It’s a free selection.
The magician removes the other bags and drinks, one by one, the transparent water in each glass.
When he removes the one that the participant has chosen, the contents are seen to be boiling, like acid or poison!