Arthashastra
कृत्वा स्कन्ध आवारस्य रक्षां वीवध आसारयोः पथश् च, परिक्षिप्य दुर्गं खात सालाभ्याम्, दूषयित्वा उदकम्, अवस्राव्य परिखाः सम्पूरयित्वा वा, सुरुङ्गा बल कुटिकाभ्यां वप्र प्राकारौ हारयेत्, दारं च गुडेन ॥
Having well guarded his camp, transports, supplies and also the roads of communication, and having dug up a ditch and raised a rampart round his camp, he may vitiate the water in the ditches round the enemy's fort, or empty the ditches of their water or fill them with water if empty, and then he may assail the rampart and the parapets by making use of underground tunnels and iron rods.
english translation
kRtvA skandha AvArasya rakSAM vIvadha AsArayoH pathaz ca, parikSipya durgaM khAta sAlAbhyAm, dUSayitvA udakam, avasrAvya parikhAH sampUrayitvA vA, suruGgA bala kuTikAbhyAM vapra prAkArau hArayet, dAraM ca guDena ॥
hk transliteration by Sanscript