“tatra pratyaya ekatanata dhyanam" - Patanjali
“Uninterrupted stream of that one point of focus is called absorption in meditation (dhyana)”

Dhyana is often mistranslated to meditation. There is no apt single word in english to capture the whole essence of dhyana. Hence the Japanese did not even attempt to translate but just called it "zen", a malformed pronunciation of this word "dhyan(a)".

Unlike the other practices explained in the past 6 chapters, this is something that cannot be practiced explicitly, but happens as a flowering of those practices. Regardless, a sadhaka (practitioner) on the path can try certain tools to facilitate this to happen. The foundation for any such practice is a right sitting posture. Padmasana (lotus pose), Vajrasana (diamond pose), Siddhasana (perfect pose) are best suited. For details on these poses, please refer: Asanas

Vippasana is a widely practiced technique to attain dhyana and eventually, the samadhi (devoid of any thought, identity or form). Anyone in the world can sign-up in dhamma.org and show-up for 10 days of practice, where food and accommodation is provided free of cost. Really! There is no catch of any kind. Lookup and try it if you can afford 10 days. Uppasana means idol worship with incantations, austerities and various other religious practices, which was widely practiced during the days of Siddhartha, a.k.a. Gauthama buddha. It was overdone to a point where the bright mind as buddha's can't take it anymore and hence he invented this technique called vippasana, which is nothing but an antonym of uppasana. In vippasana, there is no idol, no chantings, no mantras, but a very simple scientific technique that needs persistence and patience. Buddha identified the weakest link in the chain of human cycles and attacks it there to help him/her to find a way out.

By no means conclude that uppasana is bad, but overdoing anything will mask its real benefits and at times turn it against its own purpose. When done rightly, uppasana is an ultimate tool. Since it is a slippery slope, it is very easy go haywire in it. Uppasana in the past had lead to colonization, sectarianism, which eventually lead to conflicts, debates and some violent outbursts in the form of genocides. Hence simpler foolproof techniques like vippasana that can't cause much harm to the civilization is emphasized here.

Zazen is another famous technique, prominent amongst zen practitioners. This technique's essence is "the middle way". Choosing a seated pose (often vajrasana), the practitioner sways side to side to find the exact middle resting point and same by swaying forward and backward and do the same to settle the neck at its center. The eyes are neither fully closed nor fully open. Hands gesturing the dhyana mudra as shown below. Mind is brought to the center (without exerting effort) every-time it starts wandering. This is a beautiful technique and the benefits are immense, which will be conspicuous in day to day life activities of the practitioner.
Dhyana Mudra

When meditation happens to the practitioner, he/she experience a crystal clear mind, which awaits for commands to pick up a thought and churn it. At this point, mind is no more a veil, but a fine tool to explore the whole range of objects that make up the universe. It can dig deep into microscopic levels to analyze an atom or expand to experience and grasp the principles of galaxies.

All these does sound quite fictional or even philosophical, but these words don't do justice or even touch the surface of what the actual experience brings to a person. Refer to any artifact that was ever published without any commercial interest but for the benefit of mankind, it'll tell you the same thing in different ways.

Next: Yoga: 8. Samadhi (Consciousness)