First to say the speed of light

Do you know who is first to discover the speed of light?

  It's none other than  the great hindus of the Indian subcontinent.The speed of light is well mentioned in rig veda.
The fourth verse of the Rigvedic hymn 1:50 (50th hymn in book 1 of rigveda) is as follows:

तरणिर्विश्वदर्शतो जयोतिष्क्र्दसि सूर्य |
विश्वमा भासिरोचनम ||

taraNir vishvadarshato jyotishkrdasi surya |
vishvamaa bhaasirochanam ||

which means “Swift and all beautiful art thou, O Surya (Surya=Sun), maker of the light,
Illuming all the radiant realm.”

Commenting on this verse in his Rigvedic commentary, Sayana who was a minister in the court of Bukka of the great Vijayanagar Empire of Karnataka in South India (in early 14th century) says:
tatha ca smaryate yojananam. sahasre dve dve sate dve ca yojane
ekena nimishardhena kramaman.
which means “It is remembered here that Sun (light) traverses 2,202 yojanas in half a nimisha”
NOTE: Nimisharda= half of a nimisha
In the vedas Yojana is a unit of distance and Nimisha is a unit of time.

Unit of Time: Nimesa
The Moksha dharma parva of Shanti Parva in Mahabharata describes Nimisha as follows:
15 Nimisha = 1 Kastha
30 Kashta = 1 Kala
30.3 Kala = 1 Muhurta
30 Muhurtas = 1 Diva-Ratri (Day-Night)
We know Day-Night is 24 hours
So we get 24 hours = 30 x 30.3 x 30 x 15 nimisha
in other words 409050 nimisha
We know 1 hour = 60 x 60 = 3600 seconds
So 24 hours = 24 x 3600 seconds = 409050 nimisha
409050 nimesa = 86,400 seconds
1 nimesa = 0.2112 seconds (This is a recursive decimal! Wink of an eye=.2112 seconds!)
1/2 nimesa = 0.1056 seconds
Unit of Distance: Yojana
Yojana is defined in Chapter 6 of Book 1 of the ancient vedic text “Vishnu Purana” as follows
10 Paramáńus = 1 Parasúkshma
10 Parasúkshmas = 1 Trasareńu
10 Trasareńus = 1 Mahírajas (particle of dust)
10 Mahírajasas = 1 Bálágra (hair’s point)
10 Bálágras = 1 Likhyá
10 Likhyás= 1 Yúka
1o Yúkas = 1 Yavodara (heart of barley)
10 Yavodaras = 1 Yava (barley grain of middle size)
10 Yava = 1 Angula (1.89 cm or approx 3/4 inch)
6 fingers = 1 Pada (the breadth of it)
2 Padas = 1 Vitasti (span)
2 Vitasti = 1 Hasta (cubit)
4 Hastas = a Dhanu, a Danda, or pauruSa (a man’s height), or 2 Nárikás = 6 feet
2000 Dhanus = 1 Gavyúti (distance to which a cow’s call or lowing can be heard) = 12000 feet
4 Gavyútis = 1 Yojana = 9.09 miles
Calculation:
So now we can calculate what is the value of the speed of light in modern units based on the value given as 2202 yojanas in 1/2 nimesa
= 2202 x 9.09 miles per 0.1056 seconds
= 20016.18 miles per 0.1056 seconds
= 189547 miles per second !!
As per the modern science speed of light is 186000 miles per second !
And so I without the slightest doubt attribute the slight difference between the two values to our error in accurately translating from vedic units to SI/CGS units. Note that we have approximated 1 angula as exactly 3/4 inch. While the approximation is true, the angula is not exactly 3/4 inch.
NOTE: The original research in this direction was done by S.S. De and P.V. Vartak.