Valmiki Ramayana Kishkindha Kanda Sarga 41 Shloka 32

वानराः O monkeys, तं शैलम् that mountain, शिरसा bowing down your head, विमार्गत search, दुर्धर्ष: unassailable, तम् that, अतिक्रम्य beyond this, दुर्विगाहेन by a difficult one, अध्वना travelling, चतुर्दश योजनानि fourteen yojanas, सूर्यवान्नाम called Suryavanam, पर्वतः mountain.

'O monkeys bowing down to that mountain, proceed in search of Sita. O unassailable vanaras, beyond this mountain is another called Suryavan. It is at a distance of fourteen yojanas and it is difficult to cover that distance.