Arthashastra
प्रमद वन विहाराणाम् अन्यतमे वा विहार स्थाने प्रमत्तं भूमि गृह सुरुङ्गा गूढ भित्ति प्रविष्टास् तीक्ष्णा हन्युः, गूढ प्रणिहिता वा रसेन ॥
Fiery spies, hidden in an underground chamber, or in a tunnel, or inside a secret wall, may slay the enemy when the latter is carelessly amusing himself in a pleasure park or any other place of recreation; or spies under concealment may poison him.
english translation
pramada vana vihArANAm anyatame vA vihAra sthAne pramattaM bhUmi gRha suruGgA gUDha bhitti praviSTAs tIkSNA hanyuH, gUDha praNihitA vA rasena ॥
hk transliteration by Sanscript