The Sirenfish also known as the "FeJee Mermaid" was originally brought to the American Museum in 1842 "at a most extraordinary expense" for the evaluation of a "discerning public." The patchwork creature was one of P.T. Barnum's most outlandish and popular hoaxes, appealing to Americans' fascination with puzzles and enjoyment in testing illusion.

In this excerpt from his 1855 autobiography The Life of P. T. Barnum, Written by Himself, Barnum describes how he used an employee posing as a scientist and the credulity of the popular press to perpetrate the FeJee Mermaid hoax.

Early in the summer of 1842, Moses Kimball, Esq., the popular proprietor of the Boston Museum, came to New-York and exhibited to me what purported to be a mermaid. He stated that he had bought it of a sailor whose father, while in Calcutta in 1817 as captain of a Boston ship, had purchased it, believing it to be a preserved specimen of a veritable mermaid, obtained, as he was assured, from Japanese sailors. Not doubting that it would prove as surprising to others as it had been to himself, and hoping to make a rare speculation of it as an extraordinary curiosity, he appropriated $6000 of the ship's money to the purchase of it, left the ship in charge of the mate, and went to London.

He did not realize his expectations, and returned to Boston. Still believing that his curiosity was a genuine animal and therefore highly valuable, he preserved it with great care, not stinting himself in the expense of keeping it insured, though re-engaged as ship's captain under his former employers to reimburse the sum taken from their funds to pay for the mermaid. He died possessing no other property, and his only son and heir, who placed a low estimate on his father's purchase, sold it to Mr. Kimball, who brought it to New-York for my inspection.

Such was the story. Not trusting my own acuteness on such matters, I requested my naturalist's opinion of the genuineness of the animal. He replied that he could not conceive how it was manufactured; for he never knew a monkey with such peculiar teeth, arms, hands, etc., nor had he knowledge of a fish with such peculiar fins.

"Then why do you suppose it is manufactured?" I inquired.

"Because I don't believe in mermaids," replied the naturalist.

"That is no reason at all," said I, "and therefore I'll believe in the mermaid, and hire it."

This was the easiest part of the experiment. How to modify general incredulity in the existence of mermaids, so far as to awaken curiosity to see and examine the specimen, was now the all-important question. Some extraordinary means must be resorted to, and I saw no better method than to "start the ball a-rolling" at some distance from the centre of attraction.

In due time a communication appeared in the New-York Herald, dated and mailed in Montgomery, Ala., giving the news of the day, trade, the crops, political gossip, etc., and also an incidental paragraph about a certain Dr. Griffin, agent of the Lyceum of Natural History in London, recently from Pernambuco, who had in his possession a most remarkable curiosity, being nothing less than a veritable mermaid taken among the Fejee Islands, and preserved in China, where the Doctor had bought it at a high figure for the Lyceum of Natural History.

A week or ten days afterwards, a letter of similar tenor, dated and mailed in Charleston, S.C., varying of course in the items of local news, was published in another New-York paper.

This was followed by a third letter, dated and mailed in Washington city, published in still another New-York paper -- there being in addition the expressed hope that the editors of the Empire City would beg a sight of the extraordinary curiosity before Dr. Griffin took ship for England.

A few days subsequently to the publication of this thrice-repeated announcement, Mr. Lyman (who was my employee in the case of Joice Heth) was duly registered at one of the principal hotels in Philadelphia as Dr. Griffin of Pernambuco for London. His gentlemanly, dignified, yet social manners and liberality gained him a fine reputation for a few days, and when he paid his bill one afternoon, preparatory to leaving for New-York the next day, he expressed his thanks to the landlord for special attention and courtesy. "If you will step to my room," said Lyman, alias Griffin, "I will permit you to see something that will surprise you." Whereupon the landlord was shown the most extraordinary curiosity in the world -- a mermaid. He was so highly gratified and interested that he earnestly begged permission to introduce certain friends of his, including several editors, to view the wonderful specimen.

… The result might easily be gathered from the editorial columns of the Philadelphia papers a day or two subsequently to that interview with the mermaid. Suffice it to say, that the plan worked admirably, and the Philadelphia press aided the press of New-York in awakening a wide-reaching and increasing curiosity to see the mermaid.

I may as well confess that those three communications from the South were written by myself, and forwarded to friends of mine, with instructions respectively to mail them, each on the day of its date. This fact and the corresponding post-marks did much to prevent suspicion of a hoax, and the New-York editors thus unconsciously contributed to my arrangements for bringing the mermaid into public notice.