I am going by memory, but I am pretty sure it was 2% of SS tax paid. At the time I thought it was such a minuscule amount for the left to be going apoplectic over.
Which of course clearly illustrated their opposition to anything that hinted of freedom.
According to this article from 2005, it was 33.3% of the SS tax paid, with a cap of $1000. The cap was to rise 10% a year.
In 2005, the tax was 12.4% of the first $90k in wages, or $11,160. A third of that is $3720. So, you would have been able to divert $1000 to an investment account. Mice nuts, as you say.