Each engenho had a separate history, each served as a microcosm where the relations between master and slave, white and black, capital and labor were worked out. Yet, curiously, it is nearly impossible to reconstruct the operational history of any single mill. At the end of the colonial era, Bahia had more than three hundred engenhos, but the internal records of almost none of them have survived. And planters did keep accounts. They recorded the division of sugar with lavradores, kept a record of production for the tithe, and as wills indicate, knew precisely their active and passive debts. But such records have not survived for secular estates. Deeds and land titles were carefully guarded; annual accounts were not. Historian Wanderley Pinho was able to make his wonderful reconstruction of the history of Engenho Freguesia of the Rocha Pittas by weaving a few documents together around a general discussion of the Reconcavo. But he concentrated on the family's relation to the property rather than on the mill's structure and operations. For some engenhos, it is possible from wills and notarial records to trace changes of ownership, and we have occasional glimpses of internal operations from inventories made at the time of transfer. But these are momentary visions, snapshots in time, lacking continuity.