Śatapatha Brāhmaṇa ("of a hundred paths") 3.5.4.14

3.5.4.14

tānbāhumātrān khanet | anto vā eṣo 'ntenaivaitatkṛtyām mohayati tānakṣṇayā saṃtṛndanti yadyakṣṇayā na śaknuyādapi samīcastasmādime prāṇāḥ paraḥ saṃtṛṇāḥ

Let him dig them arm-deep; for that being the end (extreme limit to which he can reach) he thereby in the end brings witchcraft to naught. He connects them crossways by (underground) channels; or, if he cannot crossways, he may do so in one and the same direction. This is why these (openings of the) vital airs are connected by channels farther (inside).