Śāriputra's Cave 

Finding himself unable to control his wandering mind in meditation, the disciple asked his teacher,

“Reverend guru, I cannot meditate, no matter what I do.  Do I not have the karma to achieve this?”

And the guru replied,  “How could anyone lack the karma to meditate?  When I say that we have never been separated from innate awareness since beginningless time, do you not understand?”

The student asked,

“So, does that mean that meditation spontaneously flows forth for all living beings?”

“Although we have never been separate from meditation, we fail to recognise it.”

“What is necessary in order to recognise it?”

“You have already received the necessary introduction from your guru, but your meditation has been carried away by ghosts.”

“What manner of ghosts?” asked the terrified disciple, and the guru explained,

“When inner calm is disturbed by the ghosts of proliferating concepts, the foundation is obscured.  This happens to everyone.  Therefore you should hold fast to the root by means of signs or by means of the signless, for these two systems form the basic foundation of calm abiding meditation.  

When meditating with signs, bind your awareness firmly to the object and remain detached from conceptual thought.  

When meditating without signs, allow your awareness to remain like the open sky, free of clouds, and remain detached from conceptual thought ... ”