There was a king in Raajaa Janak's ancestors - Raajaa Nimi. It was only after Nimi that all Raajaa in that Vansh were called Janak. Down the Nimi Vansh, there was Raajaa Janak (Seetaa's father), his son was Kushdhwaj, his son was Dharmdhwaj, and Dharmdhwaj had two sons - Kritdhwaj and Mitdhwaj. Kritdhwaj had the son named Keshidhwaj and Mitdhwaj had the son named Khaandikya. This is the story of these two cousins.

Keshidhwaj was very good at Aatm Vidyaa, and Khaandikya was good at Karm Kaand. Both wanted to defeat each other. At last Keshidhwaj defeated Khaandikya and took his kingdom. After the defeat Khaandikya went to forest with his ministers and a few belongings.

Keshidhwaj was Gyaanee, but still was trying to win death by Karm (A-Vidyaa or ignorance). One day when he was doing a Yagya that a lion killed a holy cow (the cow who was used for Yagya purposes). Keshidhwaj got upset at this and asked his Braahman that what was the Praayashchit (repentance) of this. Braahman said - "We do not know, you ask Kasheru." He asked Kasheru too, but he was also not aware of this and told him to ask from Bhrigu's son Shunak Jee. Shunak Jee said - "I also do not know it, nor anybody else also knows it on this Earth, except the one who has defeated you (means Khaandikya)." Hearing this Keshidhwaj got a little worried and said - "It means I will have to go to my enemy to know about this. If he killed me I will get the fruit of my Mahaa-Yagya; or if he told me the way to do Praayashchit, then my Yagya will be complete without any hurdle."

So Raajaa Keshidhwaj wore a deer skin and went to Khaandikya. As Khaandikya saw his enemy Keshidhwaj coming, he got ready with his bow and arrow and said to him angrily - "Have you come to kill us, but today I will kill you. You have taken my kingdom, so you are a cruel king." Keshidhwaj said politely - "Hey Khaandikya, I have not come to kill you, I have come to ask a question from you." Khaandikya consulted his ministers and his ministers advised him that he should kill his enemy so that he could be the king of whole Prithvi. Khaandikya said - "You are right, after killing him I will be the King of whole Prithvi; but if I don't kill him, then I win the "Other World" and he will get only Prithvi. Now which one is greater? In my opinion the "Other World" is more important than Prithvi, rather I will tell him whatever he is asking for." So he came to Keshidhwaj and said to him - "You ask anything, I will reply you."

Raajaa Keshidhwaj told him the whole story and asked for a Praayashchit for it. Khaandikya told him the Praayshchit. Keshidhwaj came to his kingdom, completed his Yagya and thought, "I have completed my Yagya, I have given everything to everybody, everybody is satisfied, but there is something lacking, what is that?" Then he remembered that he has not given Guru Dakshinaa to Khaandikya. So he went to Khaandikya again and said to him - "Khaandikya, Since I have completed my Yagya because of you only, I have come here to give you Guru Dakshinaa. Ask me whatever you desire."

Khaandikya again consulted his ministers as what should he ask from him. His ministers again advised him to ask for his whole kingdom, wise people ask only for the kingdom without giving any trouble to their army. Khaandikya said - "How a short-lived man like me for his kingdom? You are good only to advise me on selfish interests. You do not know anything about Paramaarth?" he came to keshidhwaj and asked him - "Do you really want to give me Guru Dakshinaa." Keshidhwaj said - "Yes, That is why I have come here." Khaandikya said - "You are very knowledgeable in Adhyaatm Gyaan (spiritual knowledge) - Pramaarth Vidyaa, please tell me about that Karm (action) which can destroy my all sorrows." Keshidhwaj got very surprised to hear this, he asked - "Kshatriya ask only for kingdom, this was the best opportunity for you to ask my kingdom, why didn't you ask that?"

Khaandikya said - "Keshidhwaj, Listen to why didn't I ask you your kingdom? Only fools ask for kingdom. Although Kshatriya's Dharm is to take care of his people, and although I am Kshatriya, but since I am not a king, it is not my Dharm to take care of the people; secondly, even if I take care of the people, I will be inviting bondage with this world. Because desiring kingdom means enjoyment of pleasures which arise from greed and attachment, not from Dharm. That is why wise people do not ask for kingdom, and for the same reason I have asked you the kingdom." Keshidhwaj got very happy to hear this. He said - "I perform Yagya to win Death by A-Vidyaa, and that is how I was trying to destroy my Punya by extending the time to enjoy more pleasures. It is you good luck that wisdom dawned on you and you asked me this question. Now you listen to me about A-Vidyaa.

This A-Vidyaa, which is the seed of this world-tree, is of two types - (1) to consider other things as Aatmaa (soul), (2) and top consider the other things, which are not our own, as our own. This foolish Jeev, surrounded by the darkness of Moh (delusion), thinks that this body is "me" and "mine", while this Aatmaa is quite different from this body. Then who is that wise man who considers this body as soul? And who is that wise man who considers the pleasures of his body as his own? And who is that wise man who can consider his sons as his own?

A human being does all Karm for the pleasure of this body, and if this body is separate from "I", then what for all these Karm are? They are for this body only (excluding Aatmaa). We maintain this body by consuming Panchbhoot materials only. The dust of this Moh which has covered our Jeev, can be cleaned only by Gyaan. A-Gyaan is related to Prakriti and not to this Aatmaa. As water in a pot has no contact with fire still when a pot is kept on fire, the water becomes warm or hot or boiled; in the same way this Aatmaa becomes polluted when it comes into contact with Prakriti. This is the seed of A-Vidyaa and there is no way to destroy sorrows except Yog."

Khaandikya said - "Keshidhwaj, You know the Yog too, please tell me about Yog." Keshidhwaj said - "The only thing by which a person is bound to this world, or free from this world is his Man (mind). If the mind takes pleasure in the worldly things, one binds himself to this world, while if one does not take pleasure in these worldly things, he gets freedom (Moksh). That is why a Gyaanee person should not take pleasure in worldly things and divert his mind towards Brahm. While doing this one should follow Yam, Niyam etc (they are parts of the Yog) to change the nature of his heart. When a person's mind joins Brahm, it is called Yog."

This is very long dialog, if you are really interested in it, please read it in the Vishnu Puraan, 6/4