Holy Cross, Romanos III, with the hole of a nail from the Crucifixion

The miracle displayed in the video below is the traditional mark of authenticity of any splinter of wood which people might claim to be a segment of the true Holy Wood. The video shows a monk from Mount Athos placing the splinter of the Holy Wood in a glass of water. Initially, the splinter naturally floats, but after the monk says the Trisagion prayer, Psalms 50 and 142 , and makes the sign of the Cross three times with this splinter on the water, when he places it in the water again, the splinter sinks to the bottom. 

The monk also displays a fragrant relic of St. Haralambos towards the end for veneration.