It's not as "cool" as Facebook's $50 billion valuation from Goldman Sachs yesterday, but a New York-based private equity firm has pegged Twitter at $4.1 billion, according to the Wall Street Journal.

In an email obtained by the Journal, Felix Investments urged potential investors to partake in its "Twitter Fund," a special-purpose vehicle called Pipio Associates, which closes next week.

The fund offers a share price of $22, valuing the large start-up at $4.1 billion; $200 million more than the stance taken by a California investor last month.

"If you do not own stock in Twitter already it is a must," Felix Investments wrote in the email. "If you already own Twitter you need to add to your position. There are two absolute must have positions - Facebook and Twitter! This is the first Twitter stock we or anyone else has had in the past six months and like Facebook it will continue to trade up in price rapidly!"

Felix partner Frank Mazzola declined to comment.

Felix is simultaneously raising money for two funds with a sole holding in Facebook, Facie Libre I and II, which Dow Jones notes is a Latinate rendering of Facebook.

Filed with the Securities and Exchange Commission in 2009, the Facie Libre twins aim to raise $25 million each.

Even though Twitter and Facebook have yet to go public, funds can buy shares of the companies from former employees and other venture capital backers. Reuters blogger Felix Salmon suggested that Goldman Sachs, which is reportedly investing $450 million in Facebook, can technically trade the private shares among its high net worth clients even before Facebook goes public.