[R] Set of standard city size symbols as known from atlases?

[Werner Wernersen]

Hi,

I am wondering exists a standard set of symbols to mark cities of different size classes on a map for R yet? 

In a standard atlas there are symbols like small filled circles, small filled circles with an outer circle, same with small squares, etc. which mark capitals and different size classes of cities.

I know I can get different symbols with the pch option in plot but the question aims at if such more standard symbols of atlases are available.

Many thanks,
  Werner