Untitled — Dawn on Round Lake by Tom Thomson is going on the auction block in Calgary. (Levis Fine Art Auctions)

A rare painting by one of Canada's most celebrated artists — delivered wrapped in a towel to an auction house — will go on sale April 19 in Calgary.

Tom Thomson, who is credited with influencing the Group of Seven, created the oil painting on a hunting trip near Algonquin Park. Untitled — Dawn on Round Lake was one of four pieces Thomson painted in a single day.

He gave the piece to a doctor who was on the same trip in 1915. The oil on wood panel with a handwritten note on the back has remained in the doctor's family until recently.

The Alberta woman who owns the painting wrapped it in a towel and brought it from a small town to Calgary by bus in a half painted frame.

"She called up and said 'OK I think I want to sell it,' then I was excited," said Doug Levis, owner of Levis Fine Art Auctions, on Tuesday.

Despite current economics, Levis believes the painting will sell for about $600,000.

Because it's being sold privately, there's a chance the painting won't seen publicly again.

Calgary art collector Patrick Windle is looking forward to getting a peek at the piece.

"I think I better make sure that I get there and see it and hope that everybody else who hears about it gets there and sees it as well," he said.

Auction previews begin on the evening of April 17 at the University of Calgary, with the actual sale on April 19.

The Art Gallery of Ontario, the McMichael Canadian Art Collection and the National Gallery of Canada each have one of the other three oil paintings created by Thomson on the trip.