See two excellent articles by Rabbi David Golinkin on 'Unetaneh tokef':
http://www.schechter.edu/pubs/insight48.htm
http://www.schechter.edu/pubs/insight38.htm
The Mishnah manuscript can be viewed, courtesy of the Hebrew University, here. The word 'ki'v'numeron' can be seen six lines up from the bottom of the right-hand column.
