Bhagwad Gita
Chapter 6, Verse 8
ज्ञानविज्ञानतृप्तात्मा कूटस्थो विजितेन्द्रियः।
युक्त इत्युच्यते योगी समलोष्टाश्मकाञ्चनः।।6.8।।
A person is said to be established in self-realization and is called a yogi [or mystic] when he is fully satisfied by virtue of acquired knowledge and realization. Such a person is situated in transcendence and is self-controlled. He sees everything—whether it be pebbles, stones or gold—as the same.