The Compendium of Caraka 2.5.8

2.5.8

tato 'anantaraṃ kuṣṭhānyabhinirvartante, teṣāmidaṃ vedanāvarṇasaṃsthānaprabhāvanāmaviśeṣavijñānaṃ bhavati; tadyathā---rūkṣāruṇaparuṣāṇi viṣamavisṛtāni kharaparyantāni &tanūnyudvṛttabahistanūni &suptavatsuptāni hṛṣitalomācitāni nistodabahulānyalpakaṇḍūdāhapūyalasīkānyāśugatisamutthānānyāśubhedīni jantumanti kṛṣṇāruṇakapālavarṇāni ca kapālakuṣṭhānīti vidyāt;

Immediately thereafter, the kuṣṭhas develop. This is the diagnostic knowledge of their specific pain, colour, shape, influence, and name, namely: one should recognise as kapālakuṣṭha those that are dry, reddish-brown, rough, spreading irregularly, with harsh borders, thin, raised and thin at the exterior, numb as if dead, covered in bristled hairs, full of piercing pain, with little itching, burning, pus, and lymph, fast in progress and onset, quick to fissure, infested with organisms, and having the colour of a blackish-red potsherd.