Tiger (OS X 1.4) does not work well with Transmit. It doesn’t let you save “bookmarks”. To make it work you need to patch 2.6.2 using a tool found on the Panic.com support page. Only thing is, 2.6.2 isn’t available on the download page. Instead you need to log into ftp.panic.com (no user or password required) using Transmit (any version) and download it from the Transmit folder.
Alternatively you can download the Transmit 3 demo then FTP to panic.com and go to the archive folder that will allow you to pull from past versions (including point releases) to download.
Logging in by any other FTP client didn’t reveal this folder.