The Jataka, Volume I, tr. by Robert Chalmers, , at sacred-texts.com
"When near a village."--This was told by the Master while at Jetavana, about a lay brother who was skilled in the knowledge of fruits. It appears that a certain squire of Sāvatthi had invited the Brotherhood with the Buddha at their head, and had seated them in his pleasaunce, where they were regaled with rice-gruel and cakes. Afterwards he bade his gardener go round with the Brethren and give mangoes and other kinds of fruits to their Reverences. In obedience to orders, the man walked about the grounds with the Brethren, and could tell by a single glance up at the tree what fruit was green, what nearly ripe, and what quite ripe, and so on. And what he said was always found true. So the Brethren came to the Buddha and mentioned how expert the gardener was, and how, whilst himself standing on the ground, he could accurately tell the condition of the hanging fruit. "Brethren," said the Master, "this gardener is not the only one who has had knowledge of fruits. A like knowledge was shewn by the wise and good of former days also." And so saying, he told this story of the past.
Once on a time when Brahmadatta was reigning in Benares, the Bodhisatta was born a merchant. When he grew up, and was trading with five hundred waggons, he came one day to where the road led through a great forest.  Halting at the outskirts, he mustered the caravan and addressed them thus:--"Poison-trees grow in this forest. Take heed that you taste no unfamiliar leaf, flower, or fruit without first consulting me." All promised to take every care; and the journey into
the forest began. Now just within the forest-border stands a village, and just outside that village grows a What-fruit tree. The What-fruit tree exactly resembles a mango alike in trunk, branch, leaf, flower, and fruit. And not only in outward semblance, but also in taste and smell, the fruit--ripe or unripe--mimics the mango. If eaten, it is a deadly poison, and causes instant death.
Now some greedy fellows, who went on ahead of the caravan, came to this tree and, taking it to be a mango, ate of its fruit. But others said, "Let us ask our leader before we eat"; and they accordingly halted by the tree, fruit in hand, till he came up. Perceiving that it was no mango, he said:--"This 'mango' is a What-fruit tree; don't touch its fruit."
Having stopped them from eating, the Bodhisatta turned his attention to those who had already eaten. First he dosed them with an emetic, and then he gave them the four sweet foods to eat; so that in the end they recovered.
Now on former occasions caravans had halted beneath this same tree, and had died from eating the poisonous fruit which they mistook for mangoes. On the morrow the villagers would come, and seeing them lying there dead, would fling them by the heels into a secret place, departing with all the belongings of the caravan, waggons and all.
And on the day too of our story these villagers failed not to hurry at daybreak to the tree for their expected spoils. "The oxen must be ours," said some. "And we'll have the waggons," said others;--whilst others again claimed the wares as their share. But when they came breathless to the tree, there was the whole caravan alive and well!
"How came you to know this was not a mango-tree?" demanded the disappointed villagers. "We didn't know," said they of the caravan; "it was our leader who knew."
So the villagers came to the Bodhisatta and said, "Man of wisdom, what did you do to find out this tree was not a mango?"
"Two things told me," replied the Bodhisatta, and he repeated this stanza:-- 
And having taught the Truth to the assembled multitude, he finished his journey in safety.
"Thus, Brethren," said the Master, "in bygone days the wise and good were experts in fruit." His lesson ended, he shewed the connexion and identified the Birth by saying, "The Buddha's followers were then the people of the caravan, and I myself was the caravan leader."