The key is the use of a cup that features a hole at the bottom and small, circular magnet that rests over it. When placed on the system, the magnet is lifted up by the pressure-driven beer. The cup fills up until the weight of the liquid pushes the magnet back down over the hole. The cup can then be lifted off and the beer consumed as normal.
Wired has an article about the resurrection of a 2,550 year-old beer recipe.
Six specially constructed ditches previously excavated at Eberdingen-Hochdorf a 2,550-year-old Celtic settlement, were used to make high-quality barley malt, a key beer ingredient, says archaeobotanist Hans-Peter Stika of the University of Hohenheim in Stuttgart. Thousands of charred barley grains unearthed in the ditches about a decade ago came from a large malt-making enterprise.
Stika published his findings in Archaeological and Anthropological Sciences, where you can find the original paper.
If you’ve ever had trouble figuring out what beer to pair with your meal, the Beer Sommelier should help you. The interface is a little awkward to use, but you get what you’re looking for.