From my own independent research into the origin of the terms, "white" and "race", and specifically the terms "white race" or "white races" as applied to natural persons, the earliest primary source that I have been able to locate so far is in An Essay on the Inequality of the Human Races by Arthur de Gobineau (1853-1855)
The white races are, further, distinguished by an extraordinary attachment to life. They know better how to use it, and so, as it would seem, set a greater price on it; both in their own persons and those of others, they are more sparing of life. When they are cruel, they are conscious of their cruelty; it is very doubtful whether such a consciousness exists in the negro. At the same time, they have discovered reasons why they should surrender this busy life of theirs, that is so precious to them. The principal motive is honour, which under various names has played an enormous part in the ideas of the race from the beginning. I need hardly add that the word honour, together with all the civilizing influences connoted by it, is unknown to both the yellow and the black man… It would not have been all gain. The superiority of the white race would have been clearly shown, but it would have been bought at the price of certain advantages which have followed the mixture of blood.
Citing primary sources, what is the first documented date and attribution for the term "white race" and/or "white races" as applied to one or more natural person?