The Thomas Jefferson Papers:
Jefferson and Hemings Sources
Jefferson and Hemings Sources: Papers of John Hartwell Cocke
Cocke, a close friend of Jefferson, mentions the Jefferson-Hemings relationship twice in his diaries.
1859 April 23 (in the diary beginning 1858 March 25)
In this entry, General Cocke discusses the practice of slave owners keeping a slave woman, "as a substitute for a wife."