From a speech before the Woman's Press Club, Carnegie Hall, October 27,
1900:

To illustrate the desirability and possibility of concentration, I must tell
you a
story of my little six-year-old daughter. The governess had been teaching
her
about the reindeer, and, as the custom was, she related it to the family.
She
reduced the history of that reindeer to two or three sentences when the
governess could not have put it into a page. She said: "The reindeer is a
very
swift animal. A reindeer once drew a sled four hundred miles in two hours."
She appended the comment: "This was regarded as extraordinary." And
concluded: "When that reindeer was done drawing that sled four hundred
miles in two hours it died."

The speech is online at:

http://www.boondocksnet.com/twaintexts/speeches/mts_womanspress.html

You might also enjoy this:

Christmas with Mark Twain
http://www.boondocksnet.com/twainwww/essays/twain_christmas9712.html

Jim Zwick