Śatapatha Brāhmaṇa ("of a hundred paths") 3.1.3.12

3.1.3.12

traikakudam bhavati | yatra vā indro vṛtramahaṃstasya yadakṣyāsīttaṃ giriṃ trikakudamakarottadyattraikakudam bhavati cakṣuṣyevaitaccakṣurdadhāti tasmāttraikakudam bhavati yadi traikakudaṃ na vindedapyatraikakudameva syātsamānī hyevāñjanasya bandhutā

It is such as comes from mount Trikakud; for when Indra slew Vritra he transformed that eye of his (Vritra's) into the mount Trikakud. The reason, then, why (ointment) from mount Trikakud (is used), is that he thereby puts eye into eye. Should he be unable to obtain any Traikakuda ointment, any other than Traikakuda may be used; for one and the same, indeed, is the significance of the ointment.