Undefined property: CI_Loader::$cart

[eluser]qq71[/eluser]
This should be an easy one, but I can't figure it out.

I have this in autoload

Code:

$autoload['libraries'] = array('database', 'cart');

In my controller:

Code:

$data = array(
                       'id'      => '1234',
                       'qty'     => 1,
                       'price'   => 10.00,
                       'name'    => 'product name');
                
$this->cart->insert($data);

In my view:

Code:

echo $this->cart->format_number($this->cart->total());

I get the following error

Code:

Message:  Undefined property: CI_Loader::$cart

What am I missing?