Saturday, Wan-go H.C. Weng celebrated his 100th birthday in unusual fashion. Instead of getting presents, he chose to give one. In a ceremony at the Museum of Fine Arts, Weng presented the museum with a 53-foot-long scroll painting by Wang Hui , “10,000 Miles Along the Yangzi River (Wanli Changjiant Tu),” which dates to 1699. The painting had belonged to the Weng family since 1875. “The MFA is honored to accept this extremely generous gift from Mr. Weng,” said museum director Matthew Teitelbaum. “This masterpiece by the greatest painter of the Qing dynasty is a transformative addition to our collection.” Weng, a leading collector and connoisseur of Chinese painting, has donated nearly two dozen works to the MFA. “10,000 Miles” will be on display through Sept. 30.