Extent vs. Number

[Dan Everett]

Folks,

I am forwarding the following question from a psychologist colleague at
Florida Atlantic University. Please copy your response to the list also
to her at: iberent at science.fau.edu

Thanks,

Dan Everett

Here is the question:
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Is there a language that marks nouns for extent, rather than for
number? Because extent can be conceptually represented for either
individuals or masses, a marking for extent would treat individuals
and masses alike.  For instance, if the English plural were used to
mark extent, one could say things like "some waters" and "some
apples", and contrast them with "few water" and "few apple". Such
marking for extent should further be expected to constrain syntactic
agreement, in parallel to number agreement.

Are such systems attested?

Thanks,

Iris Berent