b. 18 September 1752 Paris
d. 9 January 1833 Paris
There were a number of different methods proposed to find the most likely value of a measured quantity. Legendre proposed the method of least squares. This appeared on pages 72-75 of the appendix to his work Nouvelles Méthodes pour la Detérmination des Orbites des Comètes published in 1805. The remainder of the appendix applies the technique to the measure of the degrees of the meridian.
In 1814 this Appendix was reprinted as "Méthode des moindres quarés," Mémoires de la Classe des Sciences Mathématiques et Physiques de l'Institut (2nd part), pp. 149-154.
A translation of the Appendix into English by George Harvey was published in The Edinburgh Philosophical Journal Vol 7. Pages 292-301.
By 1820 we have Nouvelles méthodes pour la détermination de l'orbite des comètes. Second supplement. Paris.