Nokogiri: CSS syntax for XML namespaces

Copy<soapenv:Envelope>
  <soapenv:Body>
    <elem>
      <nest>...</nest>
    </elem> 
  </soapenv:Body>
</soapenv:Envelope>

CSS selectors are a very simple tool to select elements from a Nokogiri document. However, the colon in the XML namespace syntax does not work with CSS. When selecting namespaced elements, you need to replace their colon (soapenv:Envelope) with a pipe (soapenv|Envelope):

Copydocument = Nokogiri::XML(xml)
nest = document.at_css 'soapenv|Envelope soapenv|Body elem nest'