Arthashastra
तोय कुम्भान् कांस्य भाण्डानि वा शङ्का स्थानेषु स्थापयेत् खात अभिज्ञान अर्थम् ॥
One should place water jars or bronze vessels in locations where a breach is suspected in order to detect the presence of a tunnel.
english translation
toya kumbhAn kAMsya bhANDAni vA zaGkA sthAneSu sthApayet khAta abhijJAna artham ॥
hk transliteration by Sanscript