4 Bar numbers can be printed at regular intervals, inside a box or a circle.
11 \override Score.BarNumber #'break-visibility = #end-of-line-invisible
12 \set Score.barNumberVisibility = #(every-nth-bar-number-visible 4)
13 \override Score.BarNumber #'font-size = #2
15 \override Score.BarNumber #'stencil
16 = #(make-stencil-boxer 0.1 0.25 ly:text-interface::print)
17 \repeat unfold 5 { c1 } \bar "|"
19 \override Score.BarNumber #'stencil
20 = #(make-stencil-circler 0.1 0.25 ly:text-interface::print)
21 \repeat unfold 4 { c1 } \bar "|."