quantile function

I am trying to `cut' a continuous variable into contiguous classes
containing approximately an equal number of observations. I thought
quantile() was the appropriate function to use in order to find the
breakpoints, but I end up with classes of different sizes - see
example below. Does anybody have an explanation for that? And what is
the `recommended' way of computing what I am looking for?

Example:

ca$age

 [1] 28 42 46 45 34 44 48 45 38 45 49 45 41 46 49 46 44 48 52 48 45 50
 53 57 46
[26] 52 54 57 47 52 55 59 50 54 57 60 51 55 46 63 51 59 48 35 53 59 57
37 55 32[51] 60 43 59 37 30 47 60 38 34 48 32 38 36 49 33 42 38 58 35 43
39 59 39 43 42[76] 60 40 44

table(cut(ca$age,breaks=c(-Inf,quantile(ca$age,
seq(0,1,length=11)[-1]))))

(-Inf,35] (35,38.4] (38.4,43]   (43,45] (45,46.5] (46.5,49]   (49,52]  
(52,55] 
        9         7        10         8         5        10         7   
             7 
  (55,59]   (59,63] 
       10         5 

Thanks in advance,
Giovanni

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