Displaying the first bar number

[Daniel Johnson]

Dear list,

Because I am typesetting a fragment of a larger work, I would like to
display the bar number on the first line.  By default Lilypond does not
do so, but begins displaying it on line 2.  In ly/engraver-init.ly, we
encounter the following line:
    barNumberVisibility = #default-bar-number-visibility
and in scm/output-lib.scm we see this:
    (define-public (default-bar-number-visibility barnum) (> barnum 1))
So, it seemed like I should be able to do the following:
    \set Score.barNumberVisibility = ##t
but this has no effect.  I also tried this:
    #(define-public (default-bar-number-visibility barnum) (#t))
but, as expected, it didn't work either.

If anyone can shed light on this, I'll gladly write up a blurb on it for
inclusion in the manual.  (I searched and didn't find anything there, so
please forgive if it's there and I missed it.)  I am using version 2.6.3
on Linux.

--Daniel