How much did Cameron & Tyler Winklevoss invest in Bitcoin?

Could you elaborate on the financial details surrounding Cameron and Tyler Winklevoss's investment in Bitcoin? Specifically, I'm interested in knowing the exact amount they initially invested in this cryptocurrency. Did they make a significant upfront investment, or did they gradually increase their holdings over time? Furthermore, how has this investment performed for them over the years? Did they see significant returns, or were there periods of volatility that impacted their holdings? Understanding the specifics of their Bitcoin investment could provide valuable insights into the cryptocurrency market and its potential for investors.