Git: Two initial commits

Git: Two initial commits

I have a project which recently began using version control.
There is an older attempt at this project with completely different code,
which I want to add to version control for posterity but which is neither
an ancestor nor a descendent of the initial commit of the current master
branch.
I wish to create a new parallel branch for this with no previous history
(i.e. to have multiple "initial commits". Is this possible with Git
without having to create a second repository? The commit tree would look
something like this:
o---o---o master
\
o---o branch
o old implementation
Such that I can simply use git checkout old to access the code. It must
not be cleaned up by the garbage collector after 90 days, and may
optionally be tagged.