One of the most insightful of Gautama Buddhas teachings is called Shingyo which is the shortest of a series of 3 sutras or teachings called Prajnaparamita hridaya.
It puts in a nutshell the essence of many points of his teaching including the mdiddle way, duality and Sunya or emptyness.
The Prajna Paramita mantra,which goes with this teaching is;
Gate Gate Para Gate Para Sangate Boddhi svaha!
There is a version found on audio here. Note this has the added word teyyada in the beginning.Teyyada Gate Gate Para Gate Para Sangate Boddhi svaha!
To listen on Youtube go here. It is a very calming sound.
Here is a copy of it found here where you can also find notes halfway down the page and many links to Zen teachings.
ENGLISH TRANSLATION OF THE SHINGYO
When the Bodhisattva Avalokitesvara was engaged in the practice of the deep Prajnaparamita, he perceived that there are the five Skandhas; and these he saw in their self-nature to be empty.
"O Sariputra, form is here emptiness, emptiness is form; form is no other than emptiness, emptiness is no other than form; that which is form is emptiness, that which is emptiness is form. The same can be said of sensation, thought, confection, and consciousness.
"O Sariputra, all things here are characterized with emptiness: they are not born, they are not annihilated; they are not tainted, they are not immaculate; they do not increase, they do not decrease. Therefore, O Sariputra, in emptiness there is no form, no sensation, no thought, no confection, no consciousness; no eye, ear, nose, tongue, body, mind; no form, sound, colour, taste, touch, objects; no Dhatu of vision, till we come to no Dhatu of consciousness; there is no knowledge, no ignorance," till we come to there is no old age and death, no extinction of old age and death; there is no suffering, no accumulation, no annihilation, no path; there is no knowledge, no attainment, [and] no realization,[*] because there is no attainment. In the mind of the Bodhisattva who dwells depending on the Prajnaparamita there are no obstacles;[+] and, going beyond the perverted views, he reaches final Nirvana. All the Buddhas of the past, present, and future, depending on the Prajnaparamita, attain to the highest perfect enlightenment.
1 There are two texts with the title of The Hridaya: the one is known as the Shorter and the other the Larger. The one printed above is the shorter sutra in general use in Japan and China.
The opening passage in the larger text in Sanskrit and Tibetan, which is missing in the shorter one, is as follows: [The Tibetan has this additional passage: "Adoration to the Prajnaparamita, which is beyond words, thought, and praise, whose
[* Nabhisamayah is missing in the Chinese translations as well as in the Horyuji MS.
+ For varana all the Chinese have "obstacle", and this is in full accord with the teaching of the Prajnaparamita. Max Muller's rendering, "envelop", is not good.]
self-nature is, like unto space, neither created nor destroyed, which is a state of wisdom and morality evident to our inner consciousness, and which is the mother of all Excellent Ones of the past, present, and future".] "Thus I heard. At one time World-honoured One dwelt at Rajagriha, on the Mount of the Vulture, together with a large number of Bhikshus and a large number of Bodhisattvas. At that time the World-honoured One was absorbed in a Samadhi (Meditation) known as Deep Enlightenment. And at the same moment the Great Bodhisattva Aryavalokitesvara was practising himself in the deep Prajnaparamita."
The concluding passage, which is also missing in the shorter text, runs as follows:
"O Sariputra, thus should the Bodhisattva practise himself in the deep Prajnaparamita. At that moment, the World-honoured One rose from the Samadhi and gave approval to the Great Bodhisattva Aryavalokitesvara, saying: Well done, well done, noble son! so it is! so should the practice of the deep Prajnaparamita be carried on. As it has been preached by you, it is applauded by Tathagatas and Arhats. Thus spoke the World-honoured One with joyful heart. The venerable Sariputra and the Great Bodhisattva Aryavalokitesvara together with the whole assemblage, and the world of Gods, Men, Asuras, and Gandharvas, all praised the speech of the World-honoured One."
2. From the modern scientific point of view, the conception of Skandha seems to be too vague and indefinite. But we must remember that the Buddhist principle of analysis is not derived from mere scientific interest; it aims at saving us from the idea of an ultimate individual reality which is imagined to exist as such for all the time to come. For when this idea is adhered to as final, the error of attachment is committed, and it is this attachment that forever enslaves us to the tyranny of external things. The five Skandhas ("aggregates" or "elements") are form (rupam), sensation or sense-perception (vedana), thought (samjna), confection or conformation (samskara), and consciousness (vijnana). The first Skandha is the material world or the materiality of things, while the remaining four Skandhas belong to the mind. Vedana is what we get through our senses; samjna corresponds to thought in its broadest sense, or that which mind elaborates; samskara is a very difficult term and there is no exact English equivalent; it means something that gives form, formative principle; vijnana is consciousness or mentation. There arc six forms of mentation, distinguishable as seeing, hearing, smelling, tasting, touching, and thinking.
3. Hsuan-chuang's translation has this added: "He was delivered from all suffering and misery."
4. "Empty" (sunya) or "emptiness" (sunyata) is one of the most important notions in Mahayana philosophy and at the same time the most puzzling for non-Buddhist readers to comprehend. Emptiness does not mean "relativity", or "phenomenality", or "nothingness", but rather means the Absolute, or something of transcendental nature, although this rendering is also misleading as we shall see later. When Buddhists declare all things to be empty, they are not advocating a nihilistic view; on the contrary an ultimate reality is hinted at, which cannot be subsumed under the categories of logic. With them, to proclaim the conditionality of things is to point to the existence of something altogether unconditioned and transcendent of all determination. Sunyata may thus often be most appropriately rendered by the Absolute. When the sutra says that the five Skandhas have the character of emptiness, or that in emptiness there is neither creation nor destruction, neither defilement nor immaculacy, etc., the sense is: no limiting qualities are to be attributed to the Absolute; while it is immanent in all concrete and particular objects, it is not in itself definable. Universal negation, therefore, in the philosophy of Prajna is an inevitable outcome.
5. No eye, no ear, etc., refer to the six senses. In Buddhist philosophy, mind (manovijnana) is the special sense-organ for the apprehension of dharma, or objects of thought.
6. No form, no sound, etc., are the six qualities of the external world, which become objects of the six senses.
7. "Dhatu of vision etc." refer to the eighteen Dhatus or elements of existence, which include the six senses (indriya), the six qualities (vishaya), and the six consciousnesses (vijnana).
8. "Till we come to" (yavat in Sanskrit, and nai chih in Chinese) is quite frequently met with in Buddhist literature to avoid repetition of well-known subjects. These classifications may seem somewhat confusing and overlapping.
9. "There is no knowledge, no ignorance, etc." is the wholesale denial of the Twelvefold Chain of Causation (pratityasamutpada), which are ignorance (avidya), deed (samskara), consciousness (vijnana), name and form (namarupa), six sense-organs (sadayatana), contact (sparsa), sense-perception (vedana), desire (trishna), attachment (upadana), being (bhava), birth (jati), and old age and death (jaramarana). This Chain of Twelve has been a subject of much discussion among Buddhist scholars.
10. The allusion is of course to the Fourfold Noble Truth (satya): 1. Life is suffering (duhkha); 2. Because of the accumulation (samudaya) of evil karma; 3. The cause of suffering can be annihilated (nirodha); 4. And for this there is the path (marga).