It is related that the Khalif Haroun er Reshid，being one night troubled with a persistent restlessness，summoned his Vizier Jaafer the Barmecide and said to him，My heart is straitened and I have a mind to divert myself tonight by walking about the streets of Baghdad and looking into the affairs of the folk；but we will disguise ourselves as merchants，that none may know us.'
I hear and obey，'answered Jaafer. So they rose at once and putting off the rich clothes they wore，donned merchants habits and sallied forth，the Khalif and Jaafer and Mesrour the headsman. They walked from place to place，till they came to the Tigris and saw an old man sitting in a boat；so they went up to him and saluting him，said，O old man，we desire thee of thy favour to carry us a-pleasuring down the river，in this thy boat，and take this dinar to thy hire.' Who may go a-pleasuring on the Tigris？replied the boatman. Seeing that the Khalif every night comes down the stream in his barge，and with him one crying aloud，'Ho，all ye people，great and small，gentle and simple，men and boys，whoso is found in a boat on the Tigris [by night]，I will strike off his head or hang him to the mast of his boat！'
And ye had well-nigh met him；for here comes his barge.' But the Khalif and Jaafer said，O old man，take these two dinars，and when thou seest the Khalifs barge approaching，run us under one of the arches，that we may hide there till he have passed. Hand over the money，'replied the boatman；and on God the Most High be our dependence！' So they gave him the two dinars and embarked in the boat；and he put off and rowed about with them awhile，till they saw the barge coming down the river in mid-stream，with lighted flambeaux and cressets therein. Quoth the boatman，Did I not tell you that the Khalif passed every night？O Protector，remove not the veils of Thy protection！' So saying，he ran the boat under an arch and threw a piece of black cloth over the Khalif and his companions，who looked out from under the covering and saw，in the bows of the barge，a man holding a cresset of red gold and clad in a tunic of red satin，with a muslin turban on his head. Over one of his shoulders hung a cloak of yellow brocade，and on the other was a green silk bag full of Sumatran aloes-wood，with which he fed the cresset by way of firewood. In the stern stood another man，clad like the first and bearing a like cresset，and in the barge were two hundred white slaves，standing right and left about a throne of red gold，on which sat a handsome young man，like the moon，clad in a dress of black，embroidered with yellow gold. Before him they saw a man，as he were the Vizier Jaafer，and at his head stood an eunuch，as he were Mesrour，with a drawn sword in his hand，besides a score of boon-companions. When the Khalif saw this，he turned to Jaafer and said to him，Belike this is one of my sons，El Amin or El Mamoun.' Then he examined the young man that sat on the throne，and finding him accomplished in beauty and grace and symmetry，said to Jaafer，Verily，this young man abates no jot of the state of the Khalifate！See，there stands before him one as he were thyself，O Jaafer；yonder eunuch is as he were Mesrour and those boon-companions as they were my own. By Allah，O Jaafer，my reason is confounded and I am filled with amazement at this thing！' And I also，by Allah，O Commander of the Faithful，replied Jaafer. Then the barge passed on and disappeared from sight；whereupon the boatman pushed out again into the stream，saying，Praised be God for safety，since none hath fallen in with us！' O old man，'said Er Reshid，doth the Khalif come down the river every night？Yes，O my lord，'answered the boatman；
he hath done so every night this year past.' O old man，rejoined Er Reshid，we wish thee of thy favour to await us here to-morrow night，and we will give thee five dinars，for we are strangers，lodging at El Khendek，and we have a mind to divert ourselves.' With all my heart，'replied the boatman. Then the Khalif and Jaafer and Mesrour returned to the palace，where they put off their merchants habits and donning their apparel of state，sat down each in his several room. Then came the amirs and viziers and chamberlains and officers，and the Divan assembled as of wont.
When the night came and all the folk had dispersed and gone each his own way，the Khalif said to his Vizier，Come，O Jaafer，let us go and amuse ourselves by looking on the other Khalif.' At this，Jaafer and Mesrour laughed，and the three，donning merchants habits，went out at the privy gate and made their way through the city，in great glee，till they came to the Tigris，where they found the boatman sitting，waiting for them. They embarked with him in the boat and had not sat long，before up came the mock Khalifs barge，with the cresset-bearers crying aloud as of wont，and in it two hundred white slaves other than those of the previous night. O Vizier，'exclaimed the Khalif，had I heard tell of this，I had not believed it；but I have seen it with my own eyes.' Then said he to the boatman，Take these ten dinars and row us along abreast of them，for they are in the light and we in the shade，and we can see them and divert ourselves by looking on them，but they cannot see us.' So he took the money and pushing off，followed in the shadow of the barge，till they came among the gardens and the barge cast anchor before a postern door，where they saw servants standing with a mule saddled and bridled. Here the mock Khalif landed and mounting the mule，rode away with his boon-companions，attended by his suite and preceded by the cresset-bearers crying aloud. Then Haroun and Jaafer and Mesrour landed also and making their way through the press of servants，walked on before them. Presently，the cresset-bearers espied them and seeing three strangers in merchants habits，misdoubted of them；