Not really relevant to Native American burial mounds, but Man, Myth and Magic has this in its article on giants:
Pliny relates that in the time of Claudius Caesar there was a man named Gabbaras, brought by the emperor from Arabia to Rome, who was 9 foot 9 inches high, "the tallest man that has been seen in our times". The Emperor Maximus, so the story goes, was about eight or nine feet tall and of great bulk. He was in the habit of using his wife's bracelet as a thumb ring. His shoe was a foot longer than that of any other man and his strength was so great that he was able to draw a carriage which two oxen could not move.
The following are relevant and are quoted in RD Mysteries of the Unexplained:
Human skulls with horns were found in a burial mound at Sayre, Bradford County, Pennsylvania, in the 1880's. Except for the horny projections some two inches above the eyebrows, the men to whom these skeletons belonged were anatomically normal, though at seven feet tall, well above average height. It was estimated that they were buried about A.D. 1200. The find was made by a reputable group of antiquarians, including a Pennsylvania state historian and dignitary of the Presbyterian Church (Dr. G. P. Donehoo) and two professors (A. B. Skinner of the American Investigating Museum, and W. K. Morehead of Phillips Academy, Andover, Massachusetts). Some of the bones were sent to the American Investigating Museum in Philadelphia, where they seem to have disappeared.
(Pursuit, 6:69-70, July 1973)
At the centre of one of the large Ohio burial mounds, excavators in 1891 found the skeleton of a massive man wrapped in copper armour. On the head was a copper cap, and copper moldings encased the jaws. The arms were clad in copper, and so were the chest and stomach. On either side of the head were wooden antlers encased in copper, and the mouth cavity was filled with immense but decayed pearls. Around the neck was a necklace of bear's teeth inlaid with pearls. Beside the skeleton of the giant lay that of a woman.
The remains were found at a depth of 14 feet in a mound 500 feet long, 200 feet wide, and 28 feet high.
(Nature, 45:157, December 17, 1891)
A skeleton nine feet eight inches tall was recovered from a stone burial mound at Brewersville, Indiana, in 1879. A mica necklace was around the neck, and a crude human image of burnt clay embedded with pieces of flint stood at the feet. The mound, between 3 and 5 feet high and 71 feet in diameter, was excavated by Indiana archaeologists, scientific observers from New York and Ohio, a local physician, Dr Charles Green, and the owner of the property on which the mound stood, a Mr Robinson.
The bones were kept by the Robinson family in a basket in a nearby grain mill. They were lost when a flood swept away the mill in 1937.
(The Indianapolis News, November 10, 1975)
In 1911 miners began to work the rich guano deposits in Lovelock Cave, 22 miles southwest of the Nevada town of Lovelock. They had removed several carloads of guano when they came upon some Indian relics. Soon afterward a mummy was found; reportedly it was that of a 61/2-foot-tall person with "distinctly red" hair.
According to the legends of the local Paiute Indians, a tribe of red-haired giants - the Si-te-cahs - were once the mortal enemies of the Indians in the area, who had joined forces to drive the redheads out. John T Reid of Lovelock, a mining engineer avidly interested in Indian lore, became convinced that the mummy substantiated the Paiute legend, and in the years that followed devoted himself to proving it. Included in his growing file on redheaded giants were descriptions of hair robes once worn by a few Paiutes: the hair was human and it was a reddish-brown colour.
In the meantime the discoveries at Lovelock had generated interest among archaeologists, and in 1912 the University of California at Berkeley and the Nevada State Historical Society sent Mr L. L. Loud to investigate the cave. Loud found the archaeologicaldeposits so disturbed in the rough-and-tumble of the mining operation that he only salvaged artifacts, which he took back to the University of California.
Twelve years later in 1924, the Museum of the American Indian in New York sent out a Mr M. R. Harrington to excavate the cave. He too collected artifacts and no bones. He apparently requested that one whole skeleton be reburied. Probably this was to appease the Indian employers, who were upset that such disrespectful treatment was accorded the remainsof the deceased.
But the legend of the red-haired giants persisted. In the next few years skeletal remains were found in the Lovelock area. Measuring the length of the unearthed femurs, Reid and others deduced that they belonged to a people ranging from 6 to 91/2 or 10 feet in height.
Anthropologists, however have stated that the tallest skeleton studied so far in the region was only 5 feet 11 inches, a not inconsiderable size in that time and place, but hardly a giant. Furthermore, they have pointed out, when mummies with black hair are removed from a dark cave into daylight, the hair often turns red. No-one has ben able to establish whether this happened to the Lovelock mummies.
Today a few of the remains - a skull, some bones, and artifacts - can be seen at the Humboldt Museum in Winnemucca, Nevada. Artifacts from the Lovelock area are also displayed at the Nevada State Historical Society's Museum in Reno, but no bones. And no mention is made of a giant people. Anthropologists concede however that redheaded Indians did exist in the West.
(Nevada State Historical Society Quarterly, Fall 1975, pp153 - 67; telephone interview with Amy Dansie, Nevada State Historical Society, Reno, Nevada.)
This item has a photograph of the Lovelock skull beside a 12 inch ruler, but my scanner's not working at the mo.