In Philotimus (1583), the following passage appears on page 38:
Among all forts of conceyted fellowes, I reuerence the Esseni∣ans, as most cōtinent in pleasures, & contented wt nifles, for they abhor ye company of women, & detest ye possession of gold & siluer. Thus Venus is wanton and euer is wanting, treasure is tickle, and a iuell of ieopardy, mariage marrs all, if it be out of season.
Which is basically:
Thus Venus is wanton and ever is wanting, treasure is tickle, and a jewel of jeopardy, marriage mars all, if it be out of season.
And here's the original text:
What does 'treasure is tickle' mean here?
I’ve found enough through my own research that I have at least a guess at it, which I’ll post as an answer, but I’m sure someone else might find more examples or have a more definitive/better theory as to what this could mean, and they should feel free to add it.
My first theory was that ‘tickle’ was a mistranscription of ‘fickle.’ This makes a bit of sense, as saying that fortune is fickle is a sentiment that many intellectuals enjoy espousing. But I can’t find that error repeated anywhere else in the text, and besides, all the other online versions I found have that same spelling. Even the original text isn't really that helpful in that respect in disambiguating this.
(It also seems to be a proverb, as it’s included here)