Catherine talks of craving (and later eats) dirt. One medical theory links pica cravings to iron deficiencies. Another theory suggests these cravings develop as an adaptive response to the way the immune system changes during pregnancy.
Catherine encounters a noble in the palace called Molotov and improvises a Molotov cocktail in front of him. However, the term Molotov cocktail was in fact not coined until 1939.
Intentional anachronism: Aunt Elizabeth refers to Peter holding a "Teddy" after his mother's death. Teddy Bears were created and named after Theodore Roosevelt in the early 20th century.