The Hole in the Wall - 1931

Mr. René D'Harnoncourt (1901-1968) is much more famous for being the curator of the Museum of Modern Art than he is for illustrating children's books. He was very interested in Mexican and South American artwork.

Hole in the Wall is available from amazon...if you have $200.

The Painted Pig is much more readily available - it was written by Annie Morrow Lindbergh's mother.
You can read a review of it Here.

Ms Dalgliesh's sense of what is "complicated" I do not trust. (Remember Benny ans His Penny?)

The cover of The Painted Pig:

Source