Tantrasara (Krishnananda) 2.p23

2.p23

ācāmedātmatattvādyaiḥ praṇavādyairdviṭhāntakairiti .
tato jale gaṅge cetyādinā tīrthamāvāhya mūlena kuśena trivāraṃ
bhūmau jalaṃ kṣipet .
tajjalena saptadhā mūrddhānamabhiṣiñcet .
tataḥ prāṇāyāmaṣaḍaṅganyāsau kṛtvā vāmahastatale jalaṃ
nidhāya dakṣiṇahastena jalamācchādya haṃ yaṃ vaṃ laṃ raṃ iti
trivāramabhimantrya, mūlamuccarangalitodakavindubhistattvamudrayā
mūrddhani saptadhābhyukṣaṇaṃ kṛtvā, śeṣajalaṃ dakṣiṇahaste
samādāya, tejorūpaṃ dhyātvā, iḍayākṛṣya, dehāntaḥpāpaṃ
prakṣālya, kṛṣṇavarṇaṃ tajjalaṃ pāparūpaṃ dhyātvā, piṅgalayā
virecya, puraḥkalpitavajraśilāyāṃ phaḍiti mantreṇa
pāpapuruṣasvarūpaṃ tajjalaṃ kṣipedityaghamarṣaṇam .
gaṅge cetyādimantraṃ tīrthe'pi paṭhet, tīrthe tadadviguṇaphalamiti
smṛteḥ .

He should sip water with [the mantras] beginning with the principle of the Self, preceded by the praṇava and ending in dvit-ṭha (svāhā).
Then, having invoked the sacred ford into the water with 'gaṅge ca...' and so forth, he should cast water onto the ground three times with the root-mantra using kuśa grass.
With that water he should sprinkle his head seven times.
Then, having performed breath-control and the placement on the six limbs, having placed water in the palm of his left hand, covered the water with his right hand, and consecrated it three times with 'haṃ yaṃ vaṃ laṃ raṃ', he should, reciting the root-mantra, sprinkle his head seven times with the drops of water falling through the tattvamudrā; having taken the remaining water in his right hand, meditated on it as luminous, drawn it in through the iḍā, washed away the sin inside his body, meditated on that water as black, identical to sin, and expelled it through the piṅgalā, he should cast that water, in the form of the Person of Sin, onto an imagined adamantine stone in front of him with the mantra 'phaṭ'—this is the eradication of sin.
He should recite the mantra 'gaṅge ca...' even at a sacred ford, because of the traditional rule: 'At a sacred ford, its fruit is twofold'.