Valmiki Ramayana Sundara Kanda Sarga 56 Shloka 13

अत्युच्चैः by the tall ones, देवदारुभिः with devadaru trees, ऊर्ध्वबाहुमिव as if with raised hands, स्थितम् standing, प्रपातजलनिर्घोषैः with the sounds of waterfalls, सर्वतः all over, प्राक्रुष्टमिव like the reverberations

With the tall devadaru trees on the mountain, it appeared as if the sages were standing with shoulders lifted up and performing penance. The sounds of waterfalls filled all over with reverberations.