Chang and Eng Bunker's Wedding Rings

Origin
Chang and Eng Bunker (May 11, 1811 – January 17, 1874) were Thai-American conjoined twin brothers whose condition and birthplace became the basis for the term "Siamese twins". They were married to non-conjoined sisters Adelaide and Sarah Anne Yates.

Effects
The rings were worn by Cheng and Eng specifically. When worn by two people, the two people can read each other's minds. Overuse will cause the two people to become conjoined.