Kautilya's Arthashastra 2.3.15

2.3.15

bahirjānubhañjanīśūlaprakarakūpakūṭāvapāta.kaṇṭakapratisarāhipṛṣṭhatālapattraśṛṅgāṭaka.śvadaṃṣṭrārgalopaskandanapādukāmbarīṣodapānakaiḥ praticchannaṃ channapathaṃ kārayet //

Outside the rampart, passages for movements shall be closed by forming obstructions such as a knee-breaker (jánubhanjaní), a trident, mounds of earth, pits, wreaths of thorns, instruments made like the tail of a snake, palm leaf, triangle, and of dog's teeth, rods, ditches filled with thorns and covered with sand, frying pans and water-pools.