“ When a man writes on a wall, his instinct leads him to write about the level of his own eyes. ”
 Arthur Conan Doyle, A Study in Scarlet (1887). copy citation

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“It is a simple calculation enough, though there is no use my boring you with figures. I had this fellow's stride both on the clay outside and on the dust within. Then I had a way of checking my calculation. When a man writes on a wall, his instinct leads him to write about the level of his own eyes. Now that writing was just over six feet from the ground. It was child's play.»
«And his age?» I asked.
«Well, if a man can stride four and a-half feet without the smallest effort, he can't be quite in the sere and yellow.” source

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