From Alberto Manguel and Gianni Guadalupi’s The Dictionary of Imaginary Places (New York: Macmillan, 1980):
SLEEPLESS CITY, in northern Nigeria. The inhabitants have the singular habit of never sleeping, and have therefore no idea of what sleep is.
The city is a particularly dangerous place for strangers. If a traveller should happen to overlook the local nocturnal custom and fall asleep – as he is probably accustomed to do at night – the natives, believing him dead, will proceed to dig a large grave and with great ceremony bury him immediately.
(A.J.N. Tremearne, Hausa Superstitions and Customs, London, 1913)