Anandakanda 1.20.91

1.20.91

<khecarīmudrā>
āsyāntarvivare jihvāṃ tālurandhre praveśayet /
viparītāṃ bhruvormadhye paśyenniścalayā dṛśā //

<Khecarīmudrā> / One should insert the tongue into the cavity inside the mouth, into the aperture of the palate, / turned backward, gazing between the eyebrows with an unmoving vision.