Carson, who was no stranger to danger and hard times as a mountaineer, recalled in his autobiography, "We found nothing of any great importance. There were no [freshwater] springs and the island was perfectly barren." Preuss was even less charitable in his diary. "We ferried with our miserable rubber boat to the island, which Fremont christened Disappointment Island because he expected game there but did not find it." Having thus unburdened himself, he turned to exploration. "We found plenty of salt and have boiled down some of it. I believe that three, or certainly four pounds of water make one pound of salt. I have never seen anything like it. We found the salt 15 feet deep near the island."

While Fremont and Preuss set up their instruments to begin the survey, Carson took the opportunity to stroll around the island. On the 800-foot summit, he rested near a schist rock formation and left his mark. Perhaps it was Bernier or Lajeunesse who stood with him, but in later years, this famous plainsman recalled: "We ascended the mountain, and under a shelving rock cut a large cross, which is there to this day." When Capt. Howard Stansbury took his survey party to the island seven years later, he noticed the cross, but had no clue as to its origin. He passed it off with just a single sentence in his famous report on the Great Salt Lake.