A single magpie is considered a sign of bad luck. A Guide to the Scientific Knowledge of Things Familiar recites an old proverb concerning the incidence of bad weather when magpies forage alone and a possible scientific explanation for this.
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If you catch a falling leaf on the first day of autumn you will not catch a cold all winter.
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Amber beads, worn as a necklace, can protect against illness or cure colds.
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An acorn at the window will keep lightning out
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When you speak of bad luck, it is said that one should always knock on wood. Also knocking when speaking of good luck apparently helps with having good luck. This is an old Celtic tradition related to belief of wood spirits.
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Placing keys on a table is considered unlucky. (Sweden)
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It's bad luck to leave a house through a different door than the one used to come into it.
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Placing a hat on the bed is, apparently, bad luck. (South Carolina)
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