On the QWERTY Keyboard Layout

From '''The Iron Whim,''' Darren Wershler-Henry

The matter on which all sources seem to agree is that whatever configuration [Christopher Latham] Sholes started with, the type bars began to collide with each other and stick when a typist of even moderate speed began to type.

... Sholes's partner James Densmore asked his son-in-law, the school superintendent for Western Pennsylvania, to prepare a list of the most common two-letter sequences in the English language. Speculation is that Sholes and Densmore then used this list to split up as many of these pairs as they could. ... no one seems to have a copy of the list or any evidence of how Sholes and Densmore implemented it.

p. 156