1886 letter from Renoir to Madame Charpentier (who is portrayed in Renoir’s Madame Charpentier with Her Children, 1878).

“The Petit exposition having ended, there remains only for me to thank you…As I hear you are not in Paris, won’t you please drop a word to Petit so that he might know if he should bring your paintings or hold it until your return. I am in Brittany in a wonderful place and I am working. A thousand good wishes to Georges and kisses to the children. Your good and sincere friend. Renoir.”

(Source: store.paulfrasercollectibles.com)