Arthashastra
तक्र यव भक्षस्य सप्त रात्राद् ऊर्ध्वं श्वेत गर्दभस्य लेण्ड यवैः सिद्धं गौर सर्षप तैलं विरूप करणम् ॥
The oil extracted from white mustard seeds mixed with the barley-corns contained in the dung of a white donkey, which has been living for more than seven nights on a diet of butter, milk and barley, causes alteration in colour.
english translation
takra yava bhakSasya sapta rAtrAd UrdhvaM zveta gardabhasya leNDa yavaiH siddhaM gaura sarSapa tailaM virUpa karaNam ॥
hk transliteration by Sanscript