Here is a table that I found in a 1922 cookbook that contains directions for making hot cereals. The cooking times look really long to me, but maybe the cereal grains were more coarsely cut or otherwise different a hundred years ago.
1922 Directions for Cooking Hot Breakfast Cereals
A Hundred Years Ago 
Goodness, yes. I soak porridge oats overnight and they cook in about 5 minutes.
That’s a lot of salt.
Boy, these are all extremely long cooking times and way too much salt. Three hours!!!!
Wow, 30 minutes for rolled oats!
I would have guessed something like fifteen minutes. Clearly, on the rare occasions I buy rolled oats, I’ve been doing it wrong.
Excuse my ignorance, but when “cornmeal” is listed, is that boiled cornmeal?
And the same with cracked wheat. Is that boiled cracked wheat?
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