The cajón de rumba is a wooden box played with the hands. The earliest Cuban rumba was played on such boxes, before the conga drums took their place.
In the 19th century, boxes of imported fish, mainly cod, arrived at the docks of Havana and Matanzas. Afro-Cuban dockworkers soon used them as drums. There were two kinds of boxes: small candle boxes and larger cod boxes. Craftsmen prepared them for playing rumba, in the solares of the dock neighbourhoods. Instead of claves, two wooden spoons were sometimes struck together.
The oldest set had two boxes; later it became a trio of three sizes. Wikipedia distinguishes:
In Matanzas the three are usually called caja, tres dos and quinto (also golpe, seis por ocho and repicador): the caja is the bass, the quinto improvises. A cajón is a rectangular box or an inverted pyramid, made of cedar, majagua, pine or plywood, and is played with bare hands.
In the late 19th century, cajones were used in the countryside and at the sugar mills to replace drums, which were scarce or forbidden. Overseers allowed them because they were not seen as musical instruments but as boxes that food was carried in. In the cities, too, cajones replaced drums at santería celebrations from the 19th century on: there were few consecrated batá sets, and a toque on cajones cost less than half around 1950. Consecrated cajones for santería celebrations are called cajones de fundamento.
The cajón al muerto (also cajón para eggun or rumba de muerto) is a festive ceremony for the non-deified ancestors, the eggun, within the Regla de Ocha. It is held often, especially in Matanzas. It is a fairly new tradition in which santería, spiritism and the Regla de Palo meet rumba. Behind it lies the proverb Ikú lobi Ocha, "the dead give birth to the saint": the dead are honoured first, then the Orishas.
The ensemble is three cajones (tres dos, caja and quinto), with clave, a chekeré, a bell and the guagua. The music includes rumba (yambú, guaguancó and columbia), bembé, Palo rhythms (makuta, yuka and palo), abakuá and Haitian merengue. Before the celebration the cajoneros play an oru seco for the dead, similar to the batá oru seco.
By the early 20th century tumbadoras had largely replaced the cajones. They are still played, though, including in modern styles such as guarapachangueo. Well-known players are Pancho Quinto, who also built the instruments, and Miguel "Angá" Díaz.
The Afro-Peruvian cajón, more common today, is similar to the Cuban one but a separate instrument.