Charak Samhita
लक्षणं सर्वमेवैतत् स्पर्शनेन्द्रियगोचरम्। स्पर्शनेन्द्रियविज्ञेयः स्पर्शो हि सविपर्ययः॥३०॥
All these attributes are perceptible by the tactile sense organ. Touch, together with its absence, is perceived by the tactile sense organ.
english translation
lakSaNaM sarvamevaitat sparzanendriyagocaram। sparzanendriyavijJeyaH sparzo hi saviparyayaH॥30॥
hk transliteration by Sanscript