Thomas Jefferson, plantation owner and inveterate record-keeper, recorded the smallest details of Monticello's economic and agricultural operations in his Farm Book. In addition to monitoring daily temperatures, supply costs, and productivity for the plantation's many endeavors, he tracked expenses related to the people he enslaved - purchase prices, offspring, food, and clothing. 

Take a look at this digitized version of Jefferson's Farm Book from the Massachusetts Historical Society. 

Sally Hemings' name comes up repeatedly in these records, though in ways that generally conceal their special relationship.