If two persons stop their ears closely, they may converse with each
other by holding a long stick between their teeth, or by resting their
teeth against them. The person who speaks may rest the stick against
his throat or his breast; or he may rest the stick, which he holds in
his teeth, against a glass tumbler or china basin into which the other
speaks. The sound may also be heard when a thread is held between the
teeth by both persons, so as to be somewhat stretched.