These traditions transmit orally, through divination corpora, praise poetry, proverb, song and the training of office holders, and they were not written down by the people who held them.
The written record therefore begins with outsiders, and the earliest substantial European accounts belong to the era of the Atlantic slave trade. They were written by people engaged in it or dependent on it, and they should be read as such. Missionary accounts follow, then colonial ethnography, which was frequently commissioned to make populations governable and which imposed categories, tribe, chief, fetish, that did not fit and are still being unpicked.
One case shows the cost with unusual clarity. The Dogon became internationally famous through a French ethnographic account of an elaborate esoteric cosmology, later the basis of claims about astronomical knowledge that circulate to this day. Subsequent fieldwork could not reproduce the account, and the episode is now a standard example of what happens when a single charismatic researcher and a small group of informants produce a system neither party would have produced alone.
From the mid twentieth century, African scholars writing about their own traditions changed the field, and their work is the appropriate starting point.
The atlas records what kind of institutions these are and reproduces neither the material held inside initiated offices nor the reconstructions that outsiders built on top of them.