The Skidi Pawnee Morning Star sacrificial ritual was a long drawn out ceremony. Pierre de Smet learned of it from two traders (Papin and Dougherty) who had been traders among the Pawnee in the early part of the 1800s. Dougherty lived among them for several years, so he would have most likely witnessed several of these events.
Life, letters and travels of Father Pierre-Jean de Smet, S.J., 1801-1873
By Pierre-Jean de Smet
Philadelphia, April 6, 1847.
Mr. J. D. Bryant
(The account of human sacrifice among the Pawnees was published as Letters XXVI, Oregon Missions, XXVIII, Missions de I'Oregon. It is dated as above in both, but addressed in French to a Father. The English, which seems to be a translation from the French, is here followed.)
In their religious ceremonies they dance, sing and pray before a bird stuffed with all kinds of roots and herbs used in their superstition. They have a fabulous tradition, which teaches them that the morning star sent this bird to their ancestors, as its representative, with orders to invoke it on all important occasions and to exhibit it in times of sacrifice. . .They are firmly persuaded that human sacrifices are most agreeable to the Great Spirit. Hence, when the Pawnee takes a prisoner and wishes to render himself acceptable to heaven, he devotes it to the morning star. At the time of sacrifice, he delivers the prisoner over into the hands of the jugglers . . . The victim in this horrid transaction was a young Sioux or Dakota girl, aged fifteen years, who had been taken prisoner by the Pawnees about six months previous to her immolation. . . and everywhere was treated, in appearance at least, rather as a fond friend than as a prisoner. It is the custom thus to prepare the victim, in order to conceal their infernal design.
The rest of the story
books.google.com/books?id=h9dYAAAAMAAJ&pg=PA978&lpg=PA978#v=onepage&q&f=trueThe Pawnee Indians
by George E. Hyde
"The Skidi had kidnapped a Ietan girl to sacrifice at planting time. Knife Chief tried to have her released after she had already been tied to a scaffold. It was then that Petalesharo, who had a reputation for courage, came to her rescue. None of the warriors attempted to stop him, when he cut her free, put her on his horse and delivered her to safety."
I paraphrased much of the following from Hyde's book.
But the next year, 1818, a Skidi warrior captured a young Spanish boy from New Mexican hunters, and they intended to use him for their spring sacrifice. When he and his party arrived home at their village, Knife Chief and Petalesharo failed to free the boy. Knife Chief then enlisted help from other Skidi chiefs, and the French trader, Papin, in an attempt to buy the boy from the warrior, and according to Hyde, Papin's offer was generous but the warrior refused, which caused Knife Chief "to spring at him with a war club", but at the last second, he withheld his blow, and instead of using violence, he offered selected items of his own personal property for a ransom payment, and the warrior agreed.
Account of an Expedition from Pittsburgh to the Rocky Mountains
Volume 2
By Edwin James, Stephen Harriman Long, Thomas Say
books.google.com/books?id=ys5jAAAAMAAJ&pg=PA79&lpg=PA79#v=onepage&q&f=trueThis excerpt is from an account from Major Long's expedition in 1819-20.
This particular event happened when they were heading west up the Platte in 1820. Dr Say's detachment had already been attacked by Pawnees seven miles north of the Kaw Villiage (at the mouth of the Blue Earth River) the year before (1819). They weren't harmed, but they were robbed of their provisions and were reportedly "humiliated" which might mean they were stripped naked. John Dougherty was with Say, but was out hunting when they were attacked by war party, so he wasn't aware of it until later.
Long's party spent the winter at Cantonment Engineer (Council Bluffs area) on the Missouri River and then continued their expedition up the Platte River to the Rockies the following spring. Dougherty, who spoke Caddoan and Siouan languages (as well as other Indian languages) managed to get the Pawnees to return the stolen goods.
As they progressed along:
"Towards evening, Sharetarish arrived with his dancers, thirty or forty in number, who were all accoutred and painted for the occasion."
And the following morning:
"After waiting a short time, we observed, at the distance of a mile before us, a great number of mounted Indians emerging suddenly, apparently from the plain itself, for we could not then see a ravine that had previously concealed them from our view. They immediately began to ride in various directions, and to perform numerous evolutions, until the whole were arranged in a widely-extended line. These rapid movements, which attracted our attention from other objects, having ceased, we perceived a small body of men in front, whose movements were independent of the others, and who were advancing at a moderate pace. When all were formed, they set forwards, slowly at first, but gradually increasing their speed as they approached, until they surrounded us at a full charge. It is impossible by description to do justice to the scene of savage magnificence that was now displayed. Between three and four hundred mounted Indians, dressed in their richest habiliments of war, were rushing around us in every direction, with streaming feathers, war weapons, and with loud shouts and yells. The few whom we had observed in advance of the main body, and whom, as they came near, we recognized to be the chief men, presented a perfect contrast to the others in their slow movements, and simplicity of dress. Courtesy obliged us to shake hands with each individual, as they came to us in succession for that purpose, nor was a single soldier of our train forgotten on this occasion by any one of them. They expressed great satisfaction on account of our visit, rubbing their breasts in token of the sincerity of this pleasure. Many remarked that the nation had been mourning for their grievous losses in a recent battle with an enemy, but that now grief should give place to rejoicing. Major O'Fallon addressed the Indians as usual, after which we again moved on towards the village. Latelesha, the grand chief, perceiving that the division of his warriors that were on our left, raised some dust on the march, ordered them all to leeward, that we might not be incommoded. Almost from the beginning of this interesting fete, our attention had been attracted to to a young man who seemed to be the leader or partizan of the warriors. He was about twenty-three years of age, of the finest form, tall, muscular, exceedingly graceful, and of a most prepossessing countenance. His head dress of war eagles' feathers, descended in a double series upon his back like wings, to his saddle croup; his shield was highly decorated, and his long lance was ornamented by a plaited casing of red and blue cloth. On inquiring of the interpreter, our admiration was augmented by learning that he was no other than Petalesharoo, with whose name and character we were already familiar."
Major Long's map