\input lua-visual-debug.sty

\hsize 3in \vsize 3in
\centerline{A centered line with \TeX}

\vskip .5in

A wonderful serenity has taken possession of my entire soul, like these sweet
mornings of spring which I enjoy with my whole heart. I am alone, and feel
the charm of existence in this spot, which was created for the bliss of souls
like mine. I am so happy, my dear friend, so absorbed in the exquisite sense
of mere tranquil existence, that I neglect my talents.

$$\int_e^x=mc^2$$

\bye