Tilopa's Pith Instructions on Mahamudra

There is an interesting site, where they have several different versions of Tilopa's Ganges Mahamudra, translated by Ken McLeod, Trungpa Rinpoche, Keith Dowman, Garma C.C. Chang, Lama Yeshe Gyamtso, Karl Brunnholzl, Rodney Devenish, and Lex Hixon. As an example of the richness, here is Chogyam Trungpa Rinpoche's version:

Homage to the Co-emergent Wisdom!
Mahamudra cannot be shown;
But for you who are devoted to the guru, who have mastered the ascetic practices
And are forbearant in suffering, intelligent Naropa,
Take this to heart, my fortunate student.
Kye-ho!
Look at the nature of the world,
Impermanent like a mirage or dream;
Even the mirage or dream does not exist.
Therefore, develop renunciation and abandon worldly activities.
Renounce servants and kin, causes of passion and aggression.
Meditate alone in the forest, in retreats, in solitary places.
Remain in the state of non-meditation.
If you attain non-attainment, then you have attained mahamudra.
The dharma of samsara is petty, causing passion and aggression.
The things we have created have no substance; therefore, seek the substance of the ultimate.
The dharma of mind cannot see the meaning of transcendent mind.
The dharma of action cannot discover the meaning of non-action.
If you would attain the realization of transcendent mind and non-action,
Then cut the root of mind and let consciousness remain naked.
Let the polluted waters of mental activities clear.
Do not seek to stop projections, but let them come to rest of themselves.
If there is no rejection or accepting, then you are liberated in the mahamudra.
When trees grow leaves and branches,
If you cut the roots, the many leaves and branches wither.
Likewise, if you cut the root of mind,
The various mental activities will subside.
The darkness that has collected in thousands of kalpas
One torch will dispel.
Likewise, one moment’s experience of luminous mind
Will dissolve the veil of karmic impurities.
Men of lesser intelligence who cannot grasp this,
Concentrate your awareness and focus on the breath.
Through different eye-gazes and concentration practices,
Discipline your mind until it rests naturally.
If you perceive space,
The fixed ideas of center and boundary dissolve.
Likewise, if mind perceives mind,
All mental activities will cease, you will remain in a state of non-thought,
And you will realize the supreme bodhi-citta.
Vapors arising from the earth become clouds and then vanish into the sky;
It is not known where the clouds go when they have dissolved.
Likewise, the waves of thoughts derived from the mind
Dissolve when mind perceives mind.
Space has neither color nor shape;
It is changeless, it is not tinged by black or white.
Likewise, luminous mind has neither color nor shape;
It is not tinged by black or white, virtue or vice.
The sun’s pure and brilliant essence
Cannot be dimmed by the darkness that endures for a thousand kalpas.
Likewise, the luminous essence of mind
Cannot be dimmed by the long kalpas of samsara.
Though it may be said that space is empty,
Space cannot be described.
Likewise, though it may be said that mind is luminous,
Naming it does not prove that is exists.
Space is completely without locality.
Likewise, mahamudra mind dwells nowhere.
Without change, rest loose in the primordial state;
There is no doubt that your bonds will loosen.
The essence of mind is like space;
Therefore, there is nothing which it does not encompass.
Let the movements of the body ease into genuineness,
Cease your idle chatter, let your speech become an echo,
Have no mind, but see the dharma of the leap.
The body, like a hollow bamboo, has no substance.
Mind is like the essence of space, having no place for thoughts.
Rest loose your mind; neither hold it nor permit it to wander.
If mind has no aim, it is mahamudra.
Accomplishing this is the attainment of supreme enlightenment.
The nature of mind is luminous, without object of perception.
You will discover the path of Buddha when there is no path of meditation.
By meditating on non-meditation you will attain the supreme bodhi.
This is the king of views-it transcends fixing and holding.
This is the king of meditations-without wandering mind.
This is the king of actions-without effort.
When there is no hope or fear, you have realized the goal.
The unborn alaya is without habits and veils.
Rest mind in the unborn essence; make no distinctions between meditation and post-meditation.
When projections exhaust the dharma of mind,
One attains the king of views, free from all limitations.
Boundless and deep is the supreme king of meditations.
Effortless self-existence is the supreme king of actions.
Hopeless self-existence is the supreme king of the fruition.
In the beginning mind is like a turbulent river.
In the middle it is like the River Ganges, flowing slowly.
In the end it is like the confluence of all rivers, like the meeting of mother and son.
The followers of Tantra, the Prajnaparamita,
The Vinaya, the Sutras, and other religions-
All these, by their texts and philosophical dogmas,
Will not see the luminous mahamudra.
Having no mind, without desires,
Self-quieted, self-existing,
It is like a wave of water.
Luminosity is veiled only by the rising of desire.
The real vow of samaya is broken by thinking in terms of precepts.
If you neither dwell, perceive, nor stray from the ultimate,
Then you are a holy practitioner, the torch which illuminates darkness.
If you are without desire, if you do not dwell in extremes,
You will see the dharmas of all the teachings.
If you strive in this endeavor, you will free yourself from samsaric imprisonment.
If you meditate in this way, you will burn the veil of karmic impurities.
Therefore, you are known as "The Torch of the Doctrine."
Even ignorant people who are not devoted to this teaching
Could be saved by you from constantly drowning in the river of samsara.
It is a pity that beings endure such suffering in the lower realms.
Those who would free themselves from suffering should seek a wise guru.
Being possessed by the adhishthana [blessing], one’s mind will be freed.
If you seek a karma mudra, then the wisdom of the joy of union and emptiness will arise.
The union of skillful means and knowledge brings blessings.
Bring it down and give rise to the mandala.
Deliver it to the places and distribute it throughout the body.
If there is no desire involved, then the union of joy and emptiness will arise.
Gain long life, without white hairs, and you will wax like the moon.
Become radiant, and your strength will be perfect.
Having speedily achieved the relative siddhis, one should seek the absolute siddhis.
May this pointed instruction in mahamudra remain in the hearts of fortunate beings.

Oral instructions on Mahamudra given by Sri Tilopa to Naropa at the banks of the Ganges River. Translated from the Sanskrit into Tibetan by Chokyi Lodro Marpa the Translator. English translation by Chogyam Trungpa Rinpoche in The Myth of Freedom.