Virender Sehwag's astonishing unbeaten 284 took India to 443-1 in reply to Sri Lanka's 393 after just two days of the final Test at the Brabourne Stadium.
Sehwag scored his runs off 239 balls. It was the second fastest double ton in Test history, and the fastest 250.
Only Sri Lanka's slow over-rate stopped him having a stab at Don Bradman's record haul in a day's play, 309.
But he remains on course to be the first man ever to hit three triple centuries in Test cricket.
By scoring 16 more runs on Friday, he would go ahead of Bradman and West Indian Brian Lara (who each have two) - and almost certainly break his own record for the fewest balls faced to register a Test triple ton.
Although the day began with Sri Lanka on 366-8, India - from 79 overs - recorded their best ever score in a single day's play, and much of that was down to the remarkable batting of the Delhi-born 31-year-old. Sehwag now has five of the fastest nine double hundreds in Test history, and has scored six in total.
With Sri Lanka captain Kumar Sangakkara tending to post fielders in his scoring areas on the leg-side, he showed some remarkably inventive hitting through the off-side.
Reverse-sweeps and paddles were picked off with ease, as were a succession of delightful late cuts off the quicker bowlers, and, against the spinners, drives lofted over extra cover as he backed away to the leg-side.
There were 40 boundaries and seven sixes, including some no-nonsense smacks straight down the ground and over midwicket - though he never really forced the ball, using exquisite timing and balance to keep the fielders scurrying about in vain.
He was dropped just once, by Mahela Jayawardene at slip off Tillakaratne Dilshan, by which time he had already amassed 273.
He had two partners in crime. Murali Vijay was given a rare Test appearance with Gautam Gambhir away at his sister's wedding and responded with a contribution of 87 in a 221-run opening stand before falling lbw on the sweep to Rangana Herath.
Rahul Dravid, far too good a batsman not to cash in against a demoralised bowling attack on a flat wicket, added a further 186 with Sehwag, and was 62 not out at stumps.
With three whole days of the match to come, and Sachin Tendulkar, VVS Laxman, Yuvraj Singh and Mahendra Dhoni yet to bat, India are on course for a truly eye-watering first innings score.
Amid the carnage of Thursday, Muttiah Muralitharan send down 20 overs costing 119. No itinerant observer could believe it was the same Muttiah Muralitharan who has taken a record 788 Test wickets - but such was India's confidence with the bat that he was swiftly dismantled as an attacking threat.
It had been a wretched day for Sri Lanka, who are 1-0 down in the series. Angelo Mathews seemed likely to provide an early beacon of optimism for them, but was run out by an inch as he looked for the second run he needed to reach a maiden century.
Harbhajan Singh, bowling with the sort of control that Muralitharan would strive to find, finished with 4-112 - an excellent return on an unencouraging wicket for bowlers
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