Astanga Hrudaya
वर्तिरङ्गुष्ठकस्थूला यवमध्या यथा भवेत्। छायाशुष्कां विगर्भां तां स्नेहाभ्यक्तां यथायथम्॥२०॥
it is smeared with thin paste of drugs, its thickness being that of the middle portion of the thumb. It should be dried in shade, removed of its reed, smeared with any suitable fat material (oil / ghee)
english translation
vartiraGguSThakasthUlA yavamadhyA yathA bhavet। chAyAzuSkAM vigarbhAM tAM snehAbhyaktAM yathAyatham॥20॥
hk transliteration by Sanscript