Sanseki (三石) or "three stones" is used in the game of Go to mean a three-stone advantage.
See also
Sanpitsu, a similar group of renowned calligraphers
References
Japan. Monbushō (1893). History of the Empire of Japan. Dai Nippon Tosho Kabushiki Kwaisha, by order of the Department of Education. Printed at the Japan Mail Office, Yokohama. pp.112–.