Point is like pas. It doesn't add any particular emphasis to the sentence. In modern French, we'd say :
- Le cœur a ses raisons que la raison ne connaît pas.
When, as early as the 12th century, the negation ne had to be reinforced because it had been weakened in spoken French, several words came to play this role such as pas (step), mie (crumb), goutte (drop) and point (dot) :
- Je ne marche pas.
- Je ne mange mie.
- Je ne bois goutte.
- Je ne vois point.
The various adverbs reinforcing the negation ne lost their lexical meaning very early on in Old French and did not necessarilly match semantically the verbs they were used with as explained in Eauquidort's remarks.
Pas has now superseded all the others and is the most widely used to reinforce or even to replace altogether ne. Point is considered literary or a regionalism. I remember an older guy from Ardèche telling me in conversation about the road police, Les gendarmes, j'en ai point vu.