On this day in 1749, Voltaire wrote to one of Émilie du Châtelet's friends :-
Mme du Châtelet informs you that this night, being at her desk working on Newton, she felt a little call. The little call was a daughter, who appeared in an instant. She was laid on a quarto book of geometry. The mother has gone to lie down and, if she were not asleep, she would be writing to you.Sadly, du Châtelet died 6 days later.