How can I add a child to a node at a specific position?

I have a node which has two children: an HTML text and an HTML element.

<h1 id="Installation-blahblah">Installation on server<a href="#Installation-blah" class="wiki-anchor">&para;</a>
</h1>

In this case the HTML text is:

Installation on server 

and the HTML element:

   <a href="#Installation-blah" class="wiki-anchor">anchor;</a>

I then create a node like this:

span_node = Nokogiri::HTML::Node.new('span',doc)
span_node['class'] = 'edit-section'

link_node = Nokogiri::HTML::Node.new('a',doc)
link_node['href'] = "/wiki/#{page_id}/#{@page.title}/edit?section=#{section_index}"
link_node['class'] = 'icon icon-edit'
link_node.content = 'mylink'

span_node.add_child(link_node)

Now, to add the above node to the main node I use the following:

node.add_child(span_node)

This appends the span node at the end. How can I put the span_node in front of all children?