From 5,000 New Answers to Questions, by Frederic J. Haskin, copyright 1933:
What was the largest cake every made?
Probably the largest cake was that ordered by Frederick William I, King of Prussia, in June, 1730. It is said that this contained 36 bushels of flour, 200 gallons of milk, one ton of butter, one ton of yeast, and 5000 eggs. The finished cake was 18 yards long, 8 yards broad, and more than half a yard thick. It was so large that 30,000 soldiers could not eat it all.
Just in case you wondered.