On 25 June 1824 one of Wales's grandest 21st-birthday celebrations took place for Robert Williames Vaughan, the son of Merioneth's biggest resident landowner. Held on the Nannau estate, Dolgellau, 200 guests sat down to an extravagant banquet that included a huge joint of beef from the white ox of Nannau.

The white ox was commemorated in a painting by Daniel Clowes of Chester, and the horns and hoofs were made into a candelabrum. Sir Robert also had six special toasting cups made for the occasion. They were made from the wood of the Derwen Ceubren yr Ellyll, 'the hollow oak of the demon', an ancient tree at Nannau associated with Owain Glyndwr. These were subsequently cherished by the Vaughans, and are now also in Amgueddfa Cymru's collection.