Cakradatta (Cikitsasangraha) 77.23

77.23

nāyantritāṃ śirāṃ vidhyenna tiryaṅnāpyanutthitām .
nātiśītoṣṇavātābhreṣvanyatrātyayikādgadāt .. 23 ..

One should not puncture a vein that is unrestrained, nor obliquely, nor one that has not risen; / nor during excessive cold, heat, wind, or cloudiness, except in an emergency disease.