Tertullian, Apology. De Spectaculis.
With an English Translation by T.R. Glover ... Minucius Felix.
With an English Translation by Gerald H. Rendall ... . (1931; rpt. Cambridge: Harvard University Press, 1977 = Loeb Classical Library
, 250), pp. 282-283 (Tertullian, De Spectaculis
Sic ergo evenit, ut qui in publico vix necessitate vesicae tunicam levet, idem in circo aliter non exuat, nisi totum pudorem in faciem omnium intentet ...
So it comes about that a man who will scarcely lift his tunic in public for the necessities of nature, will take it off in the circus in such a way as to make a full display of himself before all ...
Glover bowdlerizes slightly. Tertullian specifies exactly which necessity he means, viz., that of the bladder (vesicae).