The locations for the ṛṣyādi nyāsa are given in the following verse in the prapañca sāra sāra saṁgraha --
ṛṣir gurutvāt śirasaiva dhāryaḥ chando'kṣaratvāt rasanāgataṁ syāt |
dhiyā'vagantavyatayā sadaiva hṛdi pradiṣṭā manudevatā ca ||
i.e. the ṛṣi is placed on the head, the chandas on the tongue, and the devatā is established in the heart.