I once asked somebody if you could really understand this thing. Here is the answer I got: A student was once brought before the master and shown an apple and an orange. After explaining that all things were actually one, and that reality was an illusion, the master held the orange up to the student and asked: "What is this?" The student replied: "They don't have oranges where you come from?". This student passed and became a master.
As second student was then brought forward and shown the apple and the orange. The master handed the apple to the student and asked: "If all is one, how is it that this apple is not an orange?". In response the student ate the apple. This student also became a master.
Here is the poem that sparked the question:
Song of the Jewel Mirror of Awareness
The teachings of thusness has been intimately conveyed by the Buddhas and Saints.
Now you have it, keep it well.
Filling a silver bowl with snow, hiding a heron in the moonlight.
When you array them, they're not the same;
When you mix them, you know where they are.
The meaning is not in the words, yet it responds to the inquiring impulse.
If you're excited, it becomes a pitfall.
If you miss it, you fall into retrospective hesitation. Turning away and touching are both wrong for it is like a mass of fire.
Just to depict it in literary form is to relegate it to defilement.
It is bright just at midnight; it doesn't appear at dawn.
It acts as a guide for beings. its use removes all pains.
Although it is not fabricated, it is not without speech.
It is like facing a jewel mirror.
Form and image behold each other-- You are not it, it is actually you.
It is like a babe in the world, in five aspects complete;
It does not come or go, nor rise nor stand.
"Baba wawa"--is there anything said or not?
Ultimately it does not apprehend anything, because its speech is not yet correct.
It is like the six lines of the double split hexagram;
The relative and absolute integrate-- Piled up, they make three;
the complete transformation makes five.
It is like the taste of the five-flavored herb, like the diamond thunderbolt.
Subtly included within the true, inquiry and response come up together.
Communing with the source and communing with the process, It includes integration and includes the road;
Merging is auspicious; do not violate it.
Naturally real yet inconceivable, It is not within the province of delusion or enlightenment.
With causal conditions, time and season, quiescently it shines bright.
In its fineness, it fits into spacelessness; In its greatness, it is utterly beyond location.
A hairsbreadth's deviation will fail to accord with the proper attunement.
Now there are sudden and gradual, in connection with which are set up basic approaches.
Once basic approaches are distinguished, then there are guiding rules.
But even though the basis is reached and the approach comprehended, True eternity still flows.
Outwardly still while inwardly moving, Like a tethered colt, a trapped rat The ancient saints pitied them, and bestowed upon them the teaching;
According to their delusions, they called black as white When erroneous imaginations cease, the acquiescent mind realizes itself.
If you want to conform to the ancient way, please observe the ancients of former times;
When about to fulfill the way of Buddhahood, one gazed at a tree for ten aeons.
Like a tiger leaving part of its prey, a horse with a white left hind leg.
Because there is the base, [There are] jewel pedestals, fine clothing;
Because there is the startlingly different, [There are] house, cat and cow.
Yi with his archer's skill, Could hit a target at a hundred paces.
But when arrowpoints meet head on, What has this to do with the power of skill?
When the wooden man begins to sing, The stone woman gets up to dance;
It's not within reach of feeling or discrimination How could it admit of consideration in thought?
A minister serves the lord, a son obeys the father.
Not obeying is not filial and not serving is no help.
Practice intimately, working within, As though a fool, like an idiot;
If you can achieve continuity,
This is called the host within the host.