Girl with a basket of eggs, first half of the 16th century, Beuckelaer Joachim, Musée de Varsovie
1 ounce 6 gros, or 53 g! Just like us! According to Buffon.
And ranging from 1 ounce 6 gros to 2 ounces 2 gros. That is, from about 53.5 g to nearly 69 g according to the Cours complet d’agriculture, in the article ŒUFS by Abbé Rozier in 1805 (slightly after the 18th century).
The variation in egg weight noted by Rozier is due to the fact that egg size varies depending on the hen’s age.
In short, there’s no need to stress about egg weight. It was the same back then.