Claim: Tanaka Hisashige, born in Kurume, Chikugo province, invented an inkstone case with a secret lock when he was eight years old.
Evidence: Tanaka was born in Kurume, Chikugo province (present-day Fukuoka prefecture) as the eldest son of a tortoise shell craftsman. At the age of eight, he invented an inkstone case with a secret lock, which required a cord to be twisted in a certain manner to open it.