Śatapatha Brāhmaṇa ("of a hundred paths") 11.5.2.6

11.5.2.6

ayamevottaro bāhuḥ śunāsīrīyam tasya yāni pañca havīṃṣi samāyīni tā imāḥ pañcāṅgulayo'tha ya eṣa upariṣṭāddhastasya saṃdhistacunāsīrīyamidaṃ vāyavyaṃ doḥ sauryaṃ tadvā aniruktam bhavati tasmāttadaniruktam

The Sunâsîrîya, doubtless, is this left arm,--the five oblations which it has in common (with the other Seasonal offerings) are these five fingers; the Sunâsîrîya is that joint of his above the hand; that (oblation) to Vâyu is this (elbow); that to Sûrya this arm: this (oblation) is indistinct, whence this (limb) also is indistinct.