The Compendium of Caraka 3.8.42

3.8.42

athaupamyam---aupamyaṃ nāma yadanyenānyasya sādṛśyamadhikṛtya prakāśanaṃ; yathā---daṇḍena daṇḍakasya, dhanuṣā dhanuḥstambhasya, iṣvāsenā++ārogyadasyeti//

Now, comparison: comparison is an explanation based on the similarity of one thing to another; for instance, [describing] daṇḍaka through a staff, tetanus through a bow, and one who confers health through an archer.