The Japan Times has an incredible article about a man who has been able to memorise Pi to 100,000 decimal places.

Pi, as we all learnt in school, is the ratio of the circumference of a circle to its diameter.  The number starts 3.141592 and the digits go on without ceasing, making it an 'irrational number' (so called because you can't write it as a fraction).

Akira Haraguchi, a retired engineer, has managed to commit this number to memory and recite it correctly to 100,000 digits.  He has previously managed to remember 54,000 digits, 68,000 digits and 83,431 digits - his current attempt is being verified by the Guinness Book of World Records.

Mr Haraguchi uses a personal system to remember the digits.  He associates each digit with a word and commits the sequence to memory as a story!  Under his system the first 15 digits are remembered as "The wife and children have gone abroad; the husband is not scared."

Perhaps the most fascinating part of this story is that for Akira this all has spiritual significance and represents his quest for eternal truth.  He observed that nothing in nature was a line and that all things in the universe rotate.  Rotation, and hence Pi, became a key concept for him.