Mencius - Book 2, Part 1, Chapter 1C

Mencius said, 'How can king Wan be matched? From T'ang to Wû-ting there had appeared six or seven worthy and sage sovereigns. The kingdom had been attached to Yin for a long time, and this length of time made a change difficult. Wû-ting had all the princes coming to his court, and possessed the kingdom as if it had been a thing which he moved round in his palm. Then, Châu was removed from Wû-ting by no great interval of time. There were still remaining some of the ancient families and of the old manners, of the influence also which had emanated from the earlier sovereigns, and of their good government. Moreover, there were the viscount of Wei and his second son, their Royal Highnesses Pî-kan and the viscount of Ch'î, and Kâo-ko, all men of ability and virtue, who gave their joint assistance to Châu in his government.

'In consequence of these things, it took a long time for him to lose the throne. There was not a foot of ground which he did not possess. There was not one of all the people who was not his subject. So it was on his side, and king Wan at his beginning had only a territory of one hundred square lî. On all these accounts, it was difficult for him immediately to attain to the royal dignity.
~ James Legge translation via nothingistic.org ~

Go here to read the introductory post to this serialized version of the Works of Mencius.