"I used to remember my brother Henry walking into a fire outdoors when he was a week old. It was remarkable in me to remember a thing like that and it was still more remarkable that I should cling to the delusion for thirty years that I did remember it -- for of course it never happened; he would not have been able to walk at that age. . . . For many years I remembered helping my grandfather drinking his whiskey when I was six weeks old but I do not tell about that any more now; I am grown old and my memory is not as active as it used to be. When I was younger I could remember anything, whether it had happened or not; but my faculties are decaying now and soon I shall be so I cannot remember any but the things that never happened."
1. Ben Yagoda, Memoir, A History (2009), called my attention to it. The passage is from The Autobiography of Mark Twain, ed. Charles Neider (New York: Harper Collins, 1990), p. 4. I read it on Google Books, but I want the physical thing for Christmas.