Planet CakePHP

I'm trying to install cakePHP on a shared hosting setup. After extracting the files to a location like ~/public_html/dev/cake and visiting the appropriate URL (in this case http://hostname/~username/dev/cake/), I receive a 404 error:

The requested URL /usr/home/username/public_html/dev/cake/app/webroot/ was not found on this server.

I suspect that the reason for this is that upon closer inspection, the absolute path to ~/public_html is not in fact /usr/home/username/public_html, but rather /usr/www/users/username/.

Here's what I've been trying (but obviously it's not working):
(~/public_html/dev/cake/app/webroot/.htaccess)

  
    RewriteEngine On  
    RewriteBase /usr/www/users/username/dev/cake/app/webroot/ 
    RewriteCond %{REQUEST_FILENAME} !-d  
    RewriteCond %{REQUEST_FILENAME} !-f  
    RewriteRule ^(.*)$ index.php?url=$1 [QSA,L]  

Unfortunately, this doesn't seem to change anything (the 404 message remains that same). Thoughts?