Cannot be perceived by the eyes - Mundaka Upanishad

 

न चक्षुषा गृह्यते नापि वाचा नान्यैर्देवैस्तपसा कर्मण वा ।
ज्ञानप्रसादेन विशुद्धसत्त्वस्ततस्तु तं पश्यते निष्कलं ध्यायमानः ॥

Cannot be perceived by the eyes, speech or other senses, nor by austerity or sacrifice. Through the grace of knowledge one gets purified, then through contemplation alone the Absolute is realised. - Mundaka Upanishad