The Brisker Rav Checks His Tefillin in a Mirror
Told that the Divrei Chaim called checking tefillin in a mirror the mark of an am ha'aretz, the Brisker Rav said he would rather be one and wear them right.
In 1934, while Rav Velvel Soloveitchik, the Brisker Rav, was staying in the resort town of Krenitz near Sanz, the locals informed him of the Divrei Chaim’s ruling that checking tefillin placement with a mirror was unnecessary. Upon hearing this, Rav Velvel responded, “I would rather be called an am ha’aretz and know that my tefillin are in the correct place.” (Uvdot VeHanhagot LeBeit Brisk, vol. 3 [5760], pp. 179-180)
Indeed, the Shu”t Beit She’arim (OC:28) recounts that the Brisker Rav and his descendants would use a mirror each day to ensure that their head tefillin were precisely positioned.