Who is a jñāni?

Ram Dass said that jñāna yoga means to use the mind to beat the mind. Exercises that are labeled as self-inquiry, self-investigation, self-attention, tracing the "I," holding the "I," being aware of awareness, or any other way you can translate ātma vichāra refer to just this.

Due to our age-old visaya vāsanās [tendencies], the mind is constantly outward focusing on objects. As one matures in the practice of traditional object meditation, where one is to hold an object such as breath, a sound, or a mantra and ignore all else, at some point, he achieves one-pointedness of the mind. This is when he is able to attend to only that object, without being swayed by distractions. 

Then, he will be drawn to investigate the subject of the experience, which is investigating to whom this experience is arising. He constantly practices this to come to the stillness that "asking" such questions brings the mind to. Eventually, the practice itself becomes the hurdle since it keeps the notion of being a practitioner alive. It subtly feeds the ego, the "I," who is practicing in order to reach enlightenment. 

Just like how you get off the vehicle after arriving at your destination, one must let go of these methods, because methods themselves become the trap. 

Now, he is fully established in being without needing any effort. Thoughts, feelings, emotions, activities, speech, and movements rise and fall just like the waves in an ocean. But he never forgets the stillness on which these waves rise and fall. He knows well that the body does activity, the mind thinks and plans, and speech happens whenever they need to happen according to one's prārabdha [destiny] and that he has no control over it. You sleep in and miss an important meeting, body's prārabdha; you run a red light and get fined for hundreds of dollars, body's prārabdha; you say something embarrassing at a presentation and an awkward moment arises, body's prārabdha. In such manner, he uses jñāna [wisdom] to deal with things that the mind finds issues with. 

He fully understands that seeking stimulation and pleasure belongs to the body and mind and that they are transient. This is why he deliberately stays in stillness, without thoughts, and alertly aware, in the moment. The deep peace and bliss that all beings crave is right here in stillness. Unlike that which comes from mental and physical stimulation, this peace is not transient. It is our very nature. Upon waking up from deep sleep, why else do you say that you slept good?

Like Bhagavan Sri Ramana Maharshi said, effort is required to come to effortlessness. All the pujās, rituals, mantras, japas, meditation, are in place to bring an "individual" to this place of effortlessness, where he is silent, still, aware, and at peace. 

Imagine you are in his hall in Tiruvanamalai, and ask Bhagavan about jñāni. 

He will simply look at you in stillness, without words. There is your answer.