<p dir="auto">Looks like a change in v3 that never made it into the docs. Form size classes are now .input-small and .input-large instead of .input-sm and .input-lg.</p>
<p dir="auto">To increase/decrease the size of form controls, you can add the classes input-lg or input-sm (at least according to the website [http://getbootstrap.com/css/#forms] - which is the most consistent solution). In the css code, however, the classes are called input-large and input-small.</p>