An interesting look at typos from a time when typewriters were still relatively new.
The typist who composes as he operates has a threefold responsibility, for as the cells of ideation respond to the command of the will while thoughts are conceived, shaped, and transmitted, the fingers must be quick to transcribe and the vision sharp as well for punctuation and mechanical detail.
The three controls must be nicely balanced, for a laxness in muscle control results in the omission of letters, sometimes even of whole words, and spacing is obliterated, one word being run into another. A laxness of visual control results in a period being placed in the middle of a sentence in place of a comma or semicolon, or of the use of a small letter instead of a capital. The period being the emphatic stop is the one most often substituted for those of finer gradation.
I had three typos (that I noticed) when transcribing that excerpt. They were all letter transpositions.
THE PSYCHOLOGY OF THE TYPEWRITER ERROR (PDF)
From July 9, 1911