A sketch of <a href="https://en.wikipedia.org/wiki/Saturn" class="extiw" title="en:Saturn">Saturn</a> by Christiaan Huygens in 1676 showing the gap later to be named the <a href="https://en.wikipedia.org/wiki/Cassini_Division" class="extiw" title="en:Cassini Division">Cassini Division</a>.
<bdi><a href="https://en.wikipedia.org/wiki/en:Christiaan_Huygens" class="extiw" title="w:en:Christiaan Huygens"><span title="Dutch mathematician, physicist and astronomer (1629–1695)">Christiaan Huygens</span></a>
</bdi>
1676
<a rel="nofollow" class="external text" href="http://www2.jpl.nasa.gov/saturn/back.html"><i>Historical Background of Saturn's Rings</i></a> at www2.jpl.nasa.gov