When the bodies of Joseph and Hyrum Smith were returned to Nauvoo following their martyrdom in Carthage, Illinois, a public funeral was held with a burial in the city cemetery. Known to only a very few, very trusted people was the fact that the caskets buried in the cemetery held only bags of sand or stone. The bodies had been removed from those caskets for secret burial.
As published in the Deseret News in 1857:
The coffins were then taken out of the boxes into the little bedroom in the northeast corner of the Mansion, and there concealed and the door locked. Bags of sand were then placed in each end of the boxes, which were then nailed up, and a mock funeral took place, and the boxes deposited in a grave with the usual ceremonies.