The world renowned version

Although the tale of the Piper has been enhanced and translated without end, there is a standard version that is probably best known. It appears in the Brothers Grimm collection "German Legends" printed in 1816. The linguist brothers title the story "The Children of Hameln."

It was the year 1284 when a strange and wondrous figure arrived in Hameln. He was attired in a coat of many colours and was taken to be a rat catcher, because he promised to free the town of a plague of rats and mice for a fixed sum of money. 

This time, it was not rats and mice that came out, but children! A great many boys and girls older than four came running, amoung them the grown-up daughter of the mayor, to be led through the Ostertor gate and into the very heart of a hill where they all disappeared. Only two children returned because they could not keep up: one was blind and could not show where the others had gone, the other dumb and not able to tell the secret. A last little boy had come back to fetch his coat and so escaped the calamity. A total of 130 children were lost.

The road, through which the children were led, was known in the middle of the eighteenth century. (Probably still today) as The Bungelose (drum, toneless, silent), because no music nor dance be allowed there. When a bride was brought to the church with music, the musicians had to remain quiet through this lane. The mountain at Hameln, where the children disappeared, is called the Poppenberg (which was also called Koppenberg), where left and right two stones in cross shape have been erected. Some say the children had been led into a cave and reappeared in Transylvania.
(Brothers Grimm, German Legends, No. 245: "The Children of Hameln")

The citizens of Hameln recorded the event in their book of records and made a tradition of dating after the year and the day of their loss. Seyfried records the 22nd, rather than the 26th of June. 

On the old city hall a rhyme was engraved:  Im Jahr 1284 na Christi gebort to Hamel worden uthgevort hundert und dreißig Kinder dasülvest geborn dorch einen Piper under den Köppen verlorn.