LONDON—Bitcoin rallied from a three-month low on Monday in a volatile session that saw investors initially selling and then buying cryptocurrencies in the wake of Tesla boss Elon Musk’s tweets about the carmaker’s bitcoin holdings. In his latest tweet, Musk said “Tesla has not sold any bitcoin.” That seeming clarification came after weekend tweets hinted that Tesla was considering or may have already sold some of its massive holdings. Musk has boosted crypto markets with his enthusiasm for the asset class, but has lately roiled trade by appearing to cool on bitcoin in favor of its one-time parody, dogecoin. The gyrations are beginning to spook even steeled traders. Bitcoin fell more than 9 percent on Monday to as low as $42,185, its lowest since Feb. 8, but rallied back to around $45,190 as of 0911 GMT. Ether, linked to the ethereum blockhain, fell to as low as $3,123.94, and then …