Valmiki Ramayana Yuddha Kanda Sarga 65 Shloka 41

अथ and then, महातेजाः extremely energetic, महाबलः endowed with mighty strength, सःकुम्भकर्णः that Kumbhakarna, दारुणम् fearful appearance, रोमहर्षणम् horripilating, अन्यत् वपुः another form, आदाय taking hold, धनुःशतपरीणाहः hundred bows in breadth, षट्छत्रसमुच्छ्रितः six hundred bows in length, शकटचक्राक्षः wheels of chariot, महापर्वतसन्निभः like a huge mountain, रौद्रः enraged, निष्पपात set out .

Assuming another fearful form, Kumbhakarna who was highly energetic, endowed with mighty strength and frightful in form, which was a hundred bows in breadth and six hundred bows in height, with eyes like wheels of chariot, enraged, seemed like a huge mountain.