Mr. Grose thus describes this custom:
"A man and woman lying on the same bed with their clothes on; an expedient practised in America on a scarcity of beds, where, on such occasions, husbands and parents frequently permitted travellers to bundle with their wives and daughters."--Dictionary of the Vulgar Tongue.
Bundling is said to be practised in Wales. Whatever may have been the custom in former times, I do not think bundling is now practised in the United States.
Mr. Masson describes a similar custom in Central Asia:
"Many of the Afghan tribes have a custom in wooing, similar to what in Wales is known as bundling-up, and which they term namzat bazé. The lover presents himself at the house of his betrothed with a suitable gift, and in return is allowed to pass the night with her, on the understanding that innocent endearments are not to be exceeded.--Journeys in Balochistan, Afghanistan, &c. Vol. III. p. 287.