how to xpath the *value* of an attribute based on valu

Hi, sorry if this has been answered a hundred times but I haven't had
much luck finding this in the archives.

For this xml:

<xtf:snippets>
   <xtf:snippet score="100" rank="1" hitNum="5">
       MS Clark Library, University of
       <xtf:hit>
           <xtf:term>California</xtf:term>
       </xtf:hit>. 40 Albion Street Broadstairs |
   </xtf:snippet>
</xtf:snippets>


... I want to write an xpath that will select  just the numeric value
of 5 for the attribute hitNum, based on its being a sibling attribute
of rank="1". However, I can't get any closer than selecting the whole
xtf:snippet element. This are a couple ways of accessing that
inadequate result:

/xtf:snippets/xtf:snippet[@rank='1']/attribute::hitNum

/xtf:snippets/xtf:snippet[@rank='1']/@hitNum

I can't seem to get it to cough up just the 5. It would seem trivial,
but neither reference books nor any website I have found addressed it.
Any clues please, thanks.

.d