A small chalk sketch by Rembrandt van Rijn (1606-1669) sold for a staggering $17.86 million, equivalent to €15.2 million, at auction at Sotheby’s on Wednesday. The unnamed buyer bid $15 million and had to pay an additional $2.86 million in auction fees.

The sale makes Young Lion Resting by far the most expensive Rembrandt sketch ever, shattering the previous record of $3.7 million for a drawing by the Dutch master. The 115 by 150 millimeter sketch sold at the lower range of what the auction house expected. Sotheby’s estimated it would sell for between $15 million and $20 million

Sotheby’s had high expectations for Young Lion Resting, as it is one of only six drawings of lions by the Dutch master and Rembrandt’s only depiction of an animal that is still in private hands. The auction house called it “the most significant drawing by Rembrandt to come to auction in a generation.”

The sketch was sold by American billionaire Thomas S. Kaplan, who had it in his Leiden Collection for two decades. Kaplan is donating the proceeds to the Panthera Foundation, which he co-founded. The foundation is committed to the conservation of large cats.

In addition to the record-breaking bid, the buyer is responsible for paying the fees associated with the auction. Sotheby’s adds a gradual fee of 27 percent to the first million dollars of a successful sale, a 22 percent fee to the next seven million dollars, and a 15 percent against any amount above that threshold. The famed auction house is due to collect $2.86 million for selling the Rembrandt drawing.