This online archive of the Dr. Seuss collection mentions Seuss's 1925/26 Oxford University Notebook.
http://https://oac.cdlib.org/findaid/ark:/13030/tf1000043t/entire_text/?fbclid=IwZXh0bgNhZW0CMTAAAR1qoxACMkpuq12N52V_mC7k ZupyeMQ8IjOHYFYqlqyj7CBpza1MaFeudes_aem_AY2clyCbEp pg-6TSg7IRbO2F1oW4j_Y2kt0yitlbRIzz0OtOk7_sSoMFVcwAGmp XJs-e4ppEjudBvrmhqCDbwLRn
Apparently there is a NYT article which discusses the Notebook but I don't have a subscription.
Information brought to you by some of my fellow Tolkienists who responded to my query elsewhere, seeing as I was too busy to suss anything out.