Answer to your comment : Well it depends, i don't know if you master the CSS selectors :
this.click('li.history:nth-of-type(2) a');
but care, it takes the second li element from its parent, so the classname doesn't filter the search (it's used just to get back the correct parent). Using xpath (or jQuery with eq() ) is more intuitive (if i remember well it's something like that with xpath):
var x = require('casper').selectXPath;
this.click(x("li[@class='layout_right'][2] a"));