At Hardwar, the janamsakhi account has Guru Nanak Dev Ji watching pilgrims throw water eastward toward the rising sun for their ancestors, and then throwing water westward himself.
Asked what he was doing, he said he was watering his fields in Punjab. Told that his water could not reach Punjab, he asked how theirs reached the sun.
It is a debating move rather than a miracle, and almost every sakhi about ritual works the same way: the practice is not condemned, it is followed to its conclusion in front of the people doing it.
The same structure appears at Kurukshetra with the cooking of meat, at Jagannath Puri with the arti, at Achal Batala with the jogis, and at Hardwar with the water.
The Guru Granth Sahib Ji makes the same arguments in the compositions, and the sakhis are those arguments turned into scenes.
Gurdwara Nanakwara at Hardwar marks the site.
The janamsakhis are not one text. The Puratan, the Bala, the Miharban and the B40 recensions carry overlapping and conflicting sets of episodes and were written down between roughly one and two centuries after the events. Which sakhi belongs to which recension is a question with a real answer and hardly anybody asks it.
Hardwar was and is a place people go to do something for the dead. The whole point of the exchange is that the man being argued with is not doing anything foolish by his own lights, and the reply does not tell him to stop. It tells him to look at what he has just taken for granted.
The story is in the janamsakhis and is one of the small set everybody knows. Its method, taking the opponent's premise and extending it until it breaks, is the method of the whole udasi corpus.