Nirvana is a state of a mind which every one can feel it. It is real and simple. Buddha always said something real, simple and understanding, not abstracted.
Because no anyone has not eliminated desires and unwholesome deeds yet, therefore nobody know what it is.
After eliminating all desires and unwholesome deeds, a mind naturally becomes unmoveable, peaceful, joyful, and not attached. That is the state of Nirvana.
We do not need to chant, read incantation, sit meditation. just eliminate all desires and unwholesome deeds. Very easy, simple and understanding.