Kamasutra 7.1.50

7.1.50

na prayuñjīta saṃdigdhān na śarīrātyayāvahān/
na jīvaghātasaṃbaddhān nāśucidravyasaṃyutān//

"The means of producing love and sexual vigor should be learnt from the science of medicine, from the Vedas, from those who are learned in the arts of magic, and from confidential relatives. No means should be tried which are doubtful in their effects, which are likely to cause injury to the body, which involve the death of animals, and which bring us in contact with impure things. Such means should only be used as are holy, acknowledged to be good, and approved of by Brahmans and friends."