Sri-bhagavan uvaca
jnana-vijnana-trptatma
kura-stho vijitendriyah
yukta ity ucyate yogi
sama-lostrasma-kancanah
Meaning: 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.
Bhagavad Gita: Established in self realization (Dhyana-yoga (Text 08, Ch 6))