सुप्रभातम् - चरकसंहिता - सूत्रस्थानम् - द्वितीयोऽध्यायः

मात्राकालाश्रया युक्तिः, सिद्धिर्युक्तौ प्रतिष्ठिता| तिष्ठत्युपरि युक्तिज्ञो द्रव्यज्ञानवतां सदा||

Therapeutic aptness or rational therapy depends on the matra (dose) and kala(time). Success of the treatment depends on yukti (rational planning). But prior to the application of yukti (rational planning) the physician should always possess complete knowledge about drugs. [16]

Cha.su.2/16