Manasara 67.10

67.10

mukhāntaṃ dvidvimātraṃ syāllambaṃ saptamiti smṛtam
tatpṛṣṭhaśiraḥpārśve tu vaktrāntaṃ rajjuṃ lambayet

To the edge of the face, there should be two digits each; it is remembered as a plumb line of seven [units]. / Behind that, at the side of the head, one should suspend a cord to the edge of the mouth.