What was the first ready to eat breakfast cereal?

Granula in 1863 is often called the first cold /ready to eat cereal. The fact that it had to be soaked all night in order to eat it doesn't sound very "ready to eat" though, does it?

The first cold breakfast cereal, Granula, was invented in the United States in 1863 by James Caleb Jackson, operator of Our Home on the Hillside which was later replaced by the Jackson Sanatorium in Dansville, New York. The cereal never became popular as the heavy bran and graham nuggets needed soaking overnight before they were tender enough to eat and were considered inconvenient.

Fortunately cereal progress marched on, and in 1879 Wheatena became a more practical cereal.

George H. Hoyt created Wheatena circa 1879, during an era when retailers would typically buy cereal (the most popular being cracked wheat, oatmeal, and cerealine) in barrel lots, and scoop it out to sell by the pound to customers. Hoyt, who had found a distinctive process of preparing wheat for cereal, sold his cereal in boxes, offering consumers a more sanitary and consumer-friendly option.

https://en.m.wikipedia.org/wiki/Breakfast_cereal#History_of_cereal_in_North_America


‘Post Grape Nuts’ were first made in 1897 and is still produced today, making it the the oldest cereal still in production.

General Foods 'Post Toasties' cereal (1904) was originally called ‘Elijah's Manna’.

James C. Jackson, a follower of Sylvester Graham (who praised the virtues of whole grain flour, which was soon to be called Graham flour) developed what he called 'Granula' in 1863. Granula was Graham flour dough baked into dry loaves, broken into chunks and baked again, and then ground into still smaller chunks. This was the first ready-to-eat breakfast cereal. (C.W. Post used basically the same recipe for Post's Grape Nuts in 1898).

By the way, 'Granola' (baked wheat, oats and corn nuggets) was developed in 1877 by Dr. John Harvey Kellogg (before he formed the cereal company with his brother). He originally called his cereal 'Granula', but was sued by Jackson, and they compromised on the name 'Granola'.
See also article on Granola.

http://www.foodreference.com/html/fbreakfastcereals.html