Under the Table.
Let the host make a wager with one of his men guests that he cannot get under the dining table or some small sidetable and stay there while his host knocks three times on the table. “Why that would take just a second! Surely I can!” He gets under the table and his host knocks once and twice and then knocks no more but proceeds to lead his guests out of the room, leaving his betting friend either to pay up, or wait indefinitely under the table for the third knock!