They were curious things, those old high-wheel machines.  You were perched away up in the air, with the feeling that you were likely at any moment to strike a pebble or something that would fling you forward with damaging results.  Frequently that is what happened.  The word “header” seems to have grown out of that early bicycling period.  Perhaps Mark Twain invented it.  He had enough experience to do it.  He always declared afterward that he invented all the new bicycle profanity that has since come into general use.  Once he wrote: 

There was a row of low stepping-stones across one end of the street, a measured yard apart.  Even after I got so I could steer pretty fairly I was so afraid of those stones that I always hit them.  They gave me the worst falls I ever got in that street, except those which I got from dogs.  I have seen it stated that no expert is quick enough to run over a dog; that a dog is always able to skip out of his way.  I think that that may be true; but I think that the reason he couldn’t run over the dog was because he was trying to.  I did not try to run over any dog.  But I ran over every dog that came along.  I think it makes a great deal of difference.  If you try to run over the dog he knows how to calculate, but if you are trying to miss him he does not know how to calculate, and is liable to jump the wrong way every time.  It was always so in my experience.  Even when I could not hit a wagon I could hit a dog that came to see me practise.  They all liked to see me practise, and they all came, for there was very little going on in our neighborhood to entertain a dog.

He conquered, measurably, that old, discouraging thing, and he and Twichell would go on excursions, sometimes as far as Wethersfield or to the tower.  It was a pleasant change, at least it was an interesting one; but bicycling on the high wheel was never a popular diversion with Mark Twain, and his enthusiasm in the sport had died before the “safety” came along.

He had his machine sent out to Elmira, but there were too many hills in Chemung County, and after one brief excursion he came in, limping and pushing his wheel, and did not try it again.

To return to Cable.  When the 1st of April (1884) approached he concluded it would be a good time to pay off his debt of gratitude for his recent entertainment in the Clemens’s home.  He went to work at it systematically.  He had a “private and confidential” circular letter printed, and he mailed it to one hundred and fifty of Mark Twain’s literary friends in Boston, Hartford, Springfield, New York, Brooklyn, Washington, and elsewhere, suggesting that they write to him, so that their letters would reach him simultaneously April 1st, asking for his autograph.  No stamps or cards were to be inclosed for reply, and it was requested that “no stranger to Mr. Clemens and no minor” should take part.  Mrs. Clemens was let into the secret, so that she would see to it that her husband did not reject his mail or commit it to the flames unopened.