What is the physical description of the Headless Horseman in Irving's short story?

In "The Legend of Sleepy Hollow" the Headless Horseman is described as the ghost of a Hessian trooper who had his head blown off by a cannonball during the Revolutionary War. The Hessians were German soldiers who fought for the British during the war. Accordingly, the ghost haunts surrounding areas near the churchyard where the body of the soldier is buried. At daybreak, it is said that the ghost hurriedly makes its way back to the cemetery grounds after a night of haunting.

Although some citizens of Sleepy Hollow have reportedly seen the headless ghost during separate occasions, we don't get a distinctive description of the ghost until later in the story. This is when Ichabod Crane leaves the party at the Van Tassel property late at night. With his head full of the ghost stories the men have been exchanging all evening, Crane is on high alert for any suspicious activity from the spirit realm. Sure enough, as Crane continues on his journey home, he finds himself gazing at what he thinks is the Headless Horseman, not far from Wiley's Swamp. The headless rider appears to be 'gigantic in height, and muffled in a cloak,...'

He appeared to be a horseman of large dimensions, and mounted on a black horse of powerful frame.

The Headless Horseman even appears to be carrying his 'head' on the pommel of his saddle. At seeing this fearful ghost, Crane is terrified. He tries to rush his horse, Gunpowder, to the church bridge, where tradition has it that the headless rider will vanish in a huge cloud of fire and brimstone. However, the bridge doesn't save him. In a moment of horrified comprehension, Crane realizes that he has to dodge the head the ghost is throwing at him. Too late, he realizes that he will not be successful.

Just then he saw the goblin rising in his stirrups, and in the very act of hurling his head at him. Ichabod endeavored to dodge the horrible missile, but too late. It encountered his cranium with a tremendous crash,—he was tumbled headlong into the dust, and Gunpowder, the black steed, and the goblin rider, passed by like a whirlwind.

As the story wraps up, we discover that Ichabod Crane is never heard from again. However, his hat and a shattered pumpkin are found close to the bridge where Ichabod supposedly disappeared. All indications point to Brom Bones as the masquerader who frightened off his rival on that fateful night:

Brom Bones, too, who, shortly after his rival's disappearance conducted the blooming Katrina in triumph to the altar, was observed to look exceedingly knowing whenever the story of Ichabod was related, and always burst into a hearty laugh at the mention of the pumpkin; which led some to suspect that he knew more about the matter than he chose to tell.