Business Insider is perpetuating the rumor that, mobile payment startup, Square and CEO Jack Dorsey are traveling around the country in order to find interested parties for a mega-round of institutional investment. Apparently Dorsey and COO Keith Rabois were spotted around Boston’s Fidelity and Baltimore’s Legg Mason, both of whom are known as big institutional investors.

Now, All Things D reports that the rumor has been confirmed by several sources. If successful, Square could be looking a a valuation of almost $4 billion. That would be pretty impressive. They were able to secure $100 million last year with just a $1 billion valuation so, anything is possible.

Square has not made an official comment on the funding round yet, but many seem to agree it’s in the works. So, it’s not official yet, but we be following Dorsey and Square to see what come of the funding round, if it is indeed true. Square has really progressed quickly with their new mobile service, and to illustrate how much interest their service’s have attracted from small business take a look at the the following chart courtesy of SplatF and Dan Frommer:

Twitter Reaction to the $4 billion valuation: