Can a client side certificate be sent along in a header?

From a MS IIS server I need to request some files. I can do that manually using curl like this:

curl --cert thecert.pem --http1.1 -i https://somehost.com/somefile.pdf

As you can see I manually provide a client side certificate along with the request. I now need to be able to do this request from the Cantaloupe image server but I can't find any option to do this in the documentation. I can however, provide headers along with the request. I don't really have experience with client side certificates, but as far as I know they cannot be placed in the header of a request.

But before I dive into the sources of Cantaloupe to make a fork and fight with Java I want to be sure that I'm right in my thinking.

Can client side certificates be defined in a request header? Or am I right in thinking that that is not possible?