Some of these pictures and descriptions may give away plot details that you might not want to know before watching the film.
This is the next to last movie directed by Robert Aldrich, known for the classic noir Kiss Me Deadly, The Dirty Dozen, What Ever Happened to Baby Jane? and plenty of other great movies. This Western comedy is not one of those great movies but it does have a rattlesnake, which is fitting since most movies with snakes in them are not award-winners. The movie stars Gene Wilder but it's better known for co-starring Harrison Ford in his period between Star Wars and Indiana Jones.
Gene Wilder is Avram, who graduates at the bottom of his class at a Yeshiva in Poland in 1850 and is sent to San Francisco to be a Rabbi there. Most of the movie is a road movie/buddy movie after Avram misses his boat and is forced to travel from Philadelphia by land where he meets Tommy (Harrison Ford) a self-described bank robber, card player, and whoremonger.
On his journey Avram is beaten robbed and stranded, robbed of his food by raccoons, tempted by a buxom woman on a train, chased by a hanging posse, captured and nearly burned alive by Indians, drugged out of his mind, forced into a gun fight, and worst of all, he's attacked by a dangerous monster - the same one that almost everybody who travels through the west in a movie encounters - that's right, a rattlesnake. The snake encounter is used for comic effect because they needed something to scare a horse. Avram's horse is startled by the snake and bolts out of control right over a cliff into a river. When Tommy sees that Avram survives the jump, he goes and jumps his horse into the river, too.
The snake we see is a live Western Diamond-backed Rattlesnake with very nice gray coloring. For the obvious reasons of the safety of the crew and of the snake it was apparently filmed away from the scene of the action. We never see it with any characters or their horses and it looks like it was filmed in somebody's back yard instead of in the brushy habitat in the background.