Magician shows two clear empty glasses and a clear solid square plate. Then one glass is placed over the other with the solid square plate between them. When the upper glass is filled to almost full capacity with milk, the glasses are covered in front by a hankerchief and a little more milk is poured in. After the handkerchief is removed, the milk has magically filled the lower glass! The now empty upper glass and clear plate are removed and the milk in the lower glass is poured into a pitcher.
Very easy to do. You supply the pitcher and milk (or other equally suitable beverage).