Anandakanda 1.10.67

1.10.67

samukhe pārade jāryaṃ vajrabījaṃ rasonmitam /
catuḥṣaṣṭyaṃśakādyaṃ ca kramāt saṃkrāmayet priye //

Diamond seed equal to the mercury should be digested into mercury that has an open mouth; / and starting from a sixty-fourth part, one should gradually cause it to penetrate, O dear one.