How to trigger a custom event to a child iframe

iframe-custom-event.js

// Parent Window
$('button').click(function(e) {
  // This doesn't work
  $('#container iframe').contents().find('body').trigger('myevent');
  // This works
  $('#container iframe').each(function(){
    this.contentWindow.$('body').trigger('myevent');
  });
});

// iframe
$(document).ready(function() {
  $(document.body).bind('myevent', function(e) {
    alert('myevent');
  });
});