Дигха Никая 1:164
SUJATOSo tassa nagarassa samantā anupariyāyapathaṁ anukkamamāno na passeyya pākārasandhiṁ vā pākāravivaraṁ vā, antamaso biḷāranikkhamanamattampi.
As he walks around the patrol path, he doesn’t see a hole or cleft in the wall, not even one big enough for a cat to slip out.