"This was proven in 1903 by J. J. Thomson who calculated that the momentum of the electrons hitting the paddle wheel would only be sufficient to turn the wheel one revolution per minute."
This is a line from Wikipedia page.
J.J Thomson measured the charge to mass ratio of electron in year 1897, and R.K Millikan measured charge of electron in year nearly about 1910 i.e. Thomson knew only the charge to mass ratio of electron in 1903.
Then how did he was able to determine the momentum of electron when he didn't knew the mass of electron ?