If someone were to ask me how to determine the day of the vernal equinox using simple means, how should I describe it to them? For example, is the following accurate? If not, what is wrong with it and what is the better simple means? Please answer both questions. Thanks.

Well, the old adage that the sun always sets in the west is true; but, what is not true is that the sun always sets in the same place. What you can do is to set up a wooden frame whose top is parallel to and level with the western horizon as you stand and look at it, always from the same spot, about 10 feet to the east of the frame. Then, every third day, you can drive a small finishing nail part way into and sticking up from the top board to mark the position at which the sun went down. You’ll need about 122 nails to cover a full year. Then, the halfway point between the nail farthest south and the nail farthest north marks the day of the equinox.

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