3.141592653589793238462643383279
I memorized it to 31 significant figures decades ago, much further than needed for any practical purposes, but as an example of a "poem." i say I know the first 31 verses of this "poem." I also memorized many physical constants and official definitions of units of measure to twelve or more significant figures (as many as were in the definition), as well as all the major warships of all the world's navies of World War II along with other trivia for many of these such as features of their design, launch and commissioning dates, and operational history.
I also know insane amounts of information about the aircraft of both World Wars, The Red Baron, The Titanic (decades before the movie came out), and other stuff too... Most of this stuff I still remember thirty or forty years after learning it. I have continued my studies on subjects that have interested me my whole life. The internet is an awesome tool for scholars of any subject.
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"When you ride over sharps, you get flats!"--The Bicycling Guitarist, May 13, 2008