Save this page to the home screen on your device of choice and see which touch icon comes up. Make sure to try it on different devices (with varying screen resolutions) and on differing firmware versions.
Here’s the code used for the touch icons:
<link rel="apple-touch-icon-precomposed" media="screen and (resolution: 163dpi)" href="//dummyimage.com/57x57.png">
<link rel="apple-touch-icon-precomposed" media="screen and (resolution: 132dpi)" href="//dummyimage.com/72x72.png">
<link rel="apple-touch-icon-precomposed" media="screen and (resolution: 326dpi)" href="//dummyimage.com/114x114.png">