In a letter to Massachusetts politician Francis C. Gray, Jefferson laid out a mathematical formula for turning Black slaves into mulattoes and ultimately into whites over generations of breeding with whites.
“You asked me in conversation what constituted a mulatto by our law? And I believe I told you 4 crossings with the whites. I looked afterwards into our law, and found it to be in these words. ‘Every person, other than a negro, of whose grandfathers or grandmothers any one shall have been a negro, shall be deemed a mulatto, and so every such person who shall have one fourth part or more of negro blood; shall in like manner be deemed a mulatto,’” Jefferson wrote, going into great detail.