According to Yoga philosophy, the Universe is made from the constituents of the five basic elements of nature(Panch Maha Bhuta), Earth(Prthvi), Water(Aap), Fire(Tejas), Air(Vayu) and Ether(Akasha). Each element possesses five attributes, Mass(Sthula), Subtlety(Suksma), Form(Svarupa), All-pervasiveness/Interpentration (Anvaya) and purpose of fruition(Arthavatva)
 
The Gross (Sthula) characteristics  of the elements are…
Earth  -> Solidity
Water  -> Fluidity
Fire     -> Heat
Air      -> Mobility
Ether  -> Volume 
 
The Subtle(Suksma) counterparts of the elements are…
Earth  -> Smell
Water -> Taste
Fire    -> Sight
Air     -> Touch
Ether -> Sound
 
The Yoga Sutras and Bhagavad Gita make the following references…
 
Yoga Sutras of Patanjali III.45
sthūla svarūpa sūkṣma anvaya arthavattva saṃyamāt bhūta jayaḥ
 
By integration on the elements – their mass, forms, subtlety, connections and purpose, the Yogi has mastery over them;
Bhagavad Gita VII.4
 bhumir apo ‘nalo vayuh kham mano buddhir eva ca ahankara
itiyam me bhinna prakrtir astadha
 
Earth, water, fire, air, ether, mind, intelligence and ego
My material energy is divided into these eight parts
—– 
This verse was relevant to the Covid Lockdown situation. 
By suppressing our day to day actions we were acting for a good cause.
Bhagavad Gita IV.18
karmaṇyakarma yaḥ paśhyed akarmaṇi cha karma yaḥ
sa buddhimān manuṣhyeṣhu sa yuktaḥ kṛitsna-karma-kṛit
 
Those who see action in inaction and inaction in action are truly wise amongst humans. Although performing all kinds of actions, they are yogis and masters of all their actions.
 —–
Bhagavad Gita Chapter III.8
niyataṁ kuru karma tvaṁ karma jyāyo hyakarmaṇaḥ
śharīra-yātrāpi cha te na prasiddhyed akarmaṇaḥ
 
Perform your duty, for Action is superior to Inaction, 
even the maintenance of your body could not be accomplished without Action
 —–
These verses clearly explains Yoga according to Bhagavad Gita
Bhagavad Gita II.48
yoga-sthaḥ kuru karmāṇi saṅgaṁ tyaktvā dhanañjaya siddhy-asiddhyoḥ samo bhūtvā samatvaṁ yoga uchyate
 
By being fixed in Yoga, O Dhananjaya (Arjuna), perform your actions, abandoning all attachment to success and failure. Such equanimity/eveness of mind(Samatvam)  is called Yoga
  
Bhagavad Gita II.48
buddhi-yukto jahatiha ubhe sukrta-duskrte
tasmad yogaya yujyasva yogah karmasu kausalam
 
In Equanimity/eveness of mind(Samatvam), one casts off in this life the effects of both good and bad actions. 
Therefore, prepare yourself for Yoga. Yoga is skill in Action 
  —–
These verses clearly explains the aim of Yoga
Bhagavad Gita II.56
duḥkheṣhv-anudvigna-manāḥ sukheṣhu vigata-spṛihaḥ
vīta-rāga-bhaya-krodhaḥ sthita-dhīr munir uchyate

 
One whose mind is not agitated in misfortune, whose desire for pleasures has disappeared.
Whose passion, fear and anger have departed. Whose meditation is steady is said to be a Yogi/Sage
 
Yoga Sutras of Patanjali I.2
yogah cittavrtti nirodhah 
Yoga is the control/stilling of the changing states of mind/consciousness
 —–
Yoga Sutras of Patanjali I.49
Tasmin sati svasa-prasvasayoh gati vicchedah pranayama
 
When asanas are accomplished, pranayama, breath control follows. This consists of the regulation of the incoming and outgoing breaths
 
Bhagavad Gita IV.29
apāne juhvati prāṇaṁ prāṇe ’pānaṁ tathāpare

prāṇāpāna-gatī ruddhvā prāṇāyāma-parāyaṇāḥ
apare niyatāhārāḥ prāṇān prāṇeṣhu juhvati
sarve ’pyete yajña-vido yajña-kṣhapita-kalmaṣhāḥ

 
Some offer inhalation into exhalation, others exhalation into inhalation
Restraining the path of inhalation and exhalation, intent on the control of the vital breath
 
Yoga Sutras of Patanjali II.54
svaviṣaya-asaṁprayoge cittasya svarūpa-anukāraḥ iva-indriyāṇāṁ pratyāhāraḥ
 
Withdrawing the senses, mind and consciousness from contact with external objects and then drawing them inwards to the self,  is Pratyahara
 
Bhagavad Gita II.58

yadā saṁharate cāyaṁ kūrmo’ṅgānīva sarvaśaḥ

indriyāṇīndriyārthebyastasya prajnā pratiṣṭitā 

One who is able to withdraw their senses from sense objects, as the tortoise draws its limbs within the shell,
is firmly fixed in perfect conscious wisdom
  —–
Lets recap our philosophical journey of the metaphysical from the previous sessions. The embodied state consists of the five sheaths (Koshas). Each has a relation to the five basic elements of nature (Pancha Maha Bhuta). These underpin our five organs of Action (Karma Indriya) and Perception (Jnana Indriya), which form the feedback system into our Mind(Manas), Intelligence(Buddhi) and Ego(Ahamkara). 
 
Physical Layer (Annamaya Kosha) -> Earth(Prthvi) -> Smell (Gandha)
Energetic Layer (Pranamaya Kosha) -> Water(Aap) -> Taste(Rasa)
Psychological Layer (Manomaya Kosha) -> Fire(Tejas) -> Sight(Rupa)
Intellectual Layer (Vijnanamaya Kosha)-> Air(Vayu) -> Touch(Sparsa)
Blissful Layer (Annandamaya Kosha)-> Ether(Akasha) ->Sound(Sabda)
 
All of the above components are governed by the interchanging modes of nature (Gunas) -> Sattva (illumination, harmony, goodness, purity), Rajas(activity, dynamic, passion, ego), Tamas (darkness, inertia, lethargy, ignorance)
 
The process of Yoga has a transforming effect on the Gunas leading the practitioner to a pure state of Sattva 
 
The Yoga Sutras and Bhagavad Gita make the following references…
 
Yoga Sutras of Patanjali II.18
 
prakāśa-kriyā-sthiti-śīlaṃ bhūta-indriya-ātmakaṃ bhoga-apavarga-arthaṃ dṛśyam
 
That which is knowable has the nature of illumination, activity and inertia (Sattva, Rajas, Tamas). It consists of the senses and the elements, and exists for the purpose of providing either liberation or experience;
Bhagavad Gita III.27
 
prakṛiteḥ kriyamāṇāni guṇaiḥ karmāṇi sarvaśhaḥ
ahankāra-vimūḍhātmā kartāham iti manyate
 
All Actions are carried out by the three modes of material nature.
Those whose mind is confused by Ego think I am the doer