Musk said he wrote the tweet regarding taking Tesla private as he drove himself on the way to the airport in his Tesla Model S. He told The New York Times that no one reviewed the tweet before he posted it. He said that he wanted to offer a roughly 20 per cent premium over where the stock had been recently trading, which would have been about $419. He decided to round up to $420 - a number that has become code for marijuana in counterculture lore, the report said. “But I was not on weed, to be clear. Weed is not helpful for productivity. There’s a reason for the word ‘stoned.’ You just sit there like a stone on weed,” he said.